Updated on 2021/10/19

写真a

 
SUDA Jun
 
Organization
Graduate School of Engineering Electronics 2 Professor
Graduate School
Graduate School of Engineering
Undergraduate School
School of Engineering Electrical Engineering, Electronics, and Information Engineering
Title
Professor
External link

Degree 1

  1. 博士(工学) ( 1997.3   京都大学 ) 

Research Interests 9

  1. 結晶欠陥

  2. 分子線エピタキシー

  3. エピタキシャル成長

  4. 電子物性

  5. 界面

  6. 点欠陥

  7. パワーデバイス

  8. 窒化アルミニウム

  9. 窒化ガリウム

Research Areas 3

  1. Nanotechnology/Materials / Crystal engineering

  2. Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electric and electronic materials

  3. Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electron device and electronic equipment

Research History 5

  1. Nagoya University   Institute of Materials and Systems for Sustainability Center for Integrated Research of Future Electronics Innovative Devices Section

    2018.4

  2. 名古屋大学大学院   工学研究科   教授

    2017.4

      More details

    Country:Japan

  3. 京都大学大学院   工学研究科   准教授

    2008.4 - 2017.3

      More details

    Country:Japan

  4. 京都大学大学院   工学研究科   講師

    2002.10 - 2008.3

      More details

    Country:Japan

  5. 京都大学大学院   工学研究科   助手

    1997.4 - 2002.9

      More details

    Country:Japan

Education 3

  1. Kyoto University   Graduate School, Division of Engineering

    1994.4 - 1997.3

      More details

    Country: Japan

  2. Kyoto University   Graduate School, Division of Engineering

    1992.4 - 1994.3

      More details

    Country: Japan

  3. Kyoto University   Faculty of Engineering

    1988.4 - 1992.3

      More details

    Country: Japan

Professional Memberships 5

  1. 応用物理学会

  2. IEEE

  3. 電気学会

  4. 電子情報通信学会

  5. 日本結晶成長学会

 

Papers 256

  1. Impact Ionization Coefficients in GaN Measured by Above- and Sub-E<inf>g</inf> Illuminations for p<sup>-</sup>/n<sup>+</sup> Junction

    Maeda T., Narita T., Yamada S., Kachi T., Kimoto T., Horita M., Suda J.

    Technical Digest - International Electron Devices Meeting, IEDM   Vol. 2019-December   2019.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Technical Digest - International Electron Devices Meeting, IEDM  

    We propose a novel method to extract impact ionization coefficients of electrons and holes using above-and sub-bandgap illuminations for a p-/n+ junction diode. For above-bandgap illumination, the light is absorbed near p-GaN surface. Then, generated minority carriers diffuse and reach the edge of the depletion layer, resulting in an electron-injected photocurrent. On the other hand, for sub-bandgap illumination, the light is selectively absorbed near the p-n junction interface by the Franz-Keldysh effect, resulting in a hole-injected photocurrent. The electron- and hole-initiated multiplication factors are obtained as the ratios of the measured photocurrents to the calculated unmultiplicated photocurrents. By analyzing the electron- and hole-initiated multiplication factors, the impact ionization coefficients of electrons and holes in GaN are extracted separately.

    DOI: 10.1109/IEDM19573.2019.8993438

    Scopus

  2. Demonstration of Conductivity Modulation in SiC Bipolar Junction Transistors With Reduced Base Spreading Resistance

    Asada Satoshi, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 66 ( 11 ) page: 4870 - 4874   2019.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    SiC bipolar junction transistors (BJTs) were fabricated based on the design criterion proposed in our previous study, which quantitatively proved the importance of decreasing a base spreading resistance. To reduce the base spreading resistance, Al+-implantation was performed in the parasitic base region. No negative influences due to the implantation damage on the current gain were confirmed when the implantation is performed sufficiently apart from the emitter mesa sidewall, the distance of which is longer than 3μ m. Since the fabricated BJTs satisfied the design criterion, clear conductivity modulation was achieved, resulting in a reduced collector-resistance, that is, 50% of the unipolar resistance. In addition, we experimentally demonstrated that the conductivity modulation in SiC BJTs could be enhanced by decreasing the base spreading resistance.

    DOI: 10.1109/TED.2019.2941884

    Web of Science

    Scopus

  3. Measurement of avalanche multiplication utilizing Franz-Keldysh effect in GaN p-n junction diodes with double-side-depleted shallow bevel termination

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    Applied Physics Letters   Vol. 115 ( 14 )   2019.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    Avalanche multiplication characteristics of GaN p-n junction diodes (PNDs) with double-side-depleted shallow bevel termination, which exhibit nearly ideal avalanche breakdown, were investigated by photomultiplication measurements using sub-bandgap light. In GaN PNDs under reverse bias conditions, optical absorption induced by the Franz-Keldysh (FK) effect is observed, resulting in a predictable photocurrent. The avalanche multiplication factors were extracted as a ratio of the measured values to the calculated FK-induced photocurrent. In addition, the temperature dependences of the avalanche multiplications were also investigated.

    DOI: 10.1063/1.5114844

    Scopus

  4. Deep-level transient spectroscopy studies of electron and hole traps in n-type GaN homoepitaxial layers grown by quartz-free hydride-vapor-phase epitaxy

    Kanegae K., Fujikura H., Otoki Y., Konno T., Yoshida T., Horita M., Kimoto T., Suda J.

    Applied Physics Letters   Vol. 115 ( 1 )   2019.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    We studied deep levels in quartz-free hydride-vapor-phase epitaxy (QF-HVPE)-grown homoepitaxial n-type GaN layers within which three electron and eight hole traps were detected. The dominant electron and hole traps observed in the QF-HVPE-grown GaN layers were E3 (EC - 0.60 eV) and H1 (EV + 0.87 eV), respectively. We found that the E3 trap density of QF-HVPE-grown GaN (∼1014 cm-3) was comparable with that of MOVPE-grown GaN layers, whereas the H1 trap density of QF-HVPE-grown GaN (∼1014 cm-3) was much smaller than that of an MOVPE-grown GaN layer with a low-residual-carbon growth condition. A detailed analysis of the QF-HVPE-grown GaN layers revealed that the H1 trap density is almost equal to the carbon impurity concentration and other impurities that compensate the Si donors besides the carbon impurity were hardly detected in the QF-HVPE-grown GaN layers.

    DOI: 10.1063/1.5098965

    Scopus

  5. Design and Fabrication of GaN p-n Junction Diodes with Negative Beveled-Mesa Termination

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    IEEE Electron Device Letters   Vol. 40 ( 6 ) page: 941 - 944   2019.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    We report on homoepitaxial GaN p-n junction diodes with a negative beveled-mesa termination. The electric field distribution in a beveled-mesa was investigated using TCAD simulation, and the devices were designed using currently available GaN growth techniques. Shallow-angle (ca. 10°) negative bevel GaN p-n junction diodes were fabricated with various Mg acceptor concentrations in the p-layers. The suppression of electric field crowding and improvement of the breakdown voltage were observed, as the Mg concentration was decreased. The parallel-plane breakdown field of 2.86 MV/cm was obtained for a device with the breakdown voltage of 425 V.

    DOI: 10.1109/LED.2019.2912395

    Scopus

  6. Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz-Keldysh Effect

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    Proceedings of the International Symposium on Power Semiconductor Devices and ICs   Vol. 2019-May   page: 59 - 62   2019.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the International Symposium on Power Semiconductor Devices and ICs  

    A valanche multiplication characteristics in GaN p-n junction diodes (PNDs) under high reverse bias conditions were investigated. The GaN-on-GaN PNDs with double-side-depleted shallow bevel termination, which showed low reverse leakage current and excellent avalanche capability, were used for the measurements. Under sub-bandgap light illumination, the photocurrents induced by Franz-Keldysh (FK) effect, which can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed. The multiplication factors were extracted as the ratios of the experimental photocurrents to the calculated FK-induced photocurrent. Under an assumption of equal impact ionization coefficients of electrons and holes, the electric-field dependence of an impact ionization coefficient in GaN were estimated.

    DOI: 10.1109/ISPSD.2019.8757676

    Scopus

  7. Parallel-Plane Breakdown Fields of 2.8-3.5 MV/cm in GaN-on-GaN p-n Junction Diodes with Double-Side-Depleted Shallow Bevel Termination

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    Technical Digest - International Electron Devices Meeting, IEDM   Vol. 2018-December   page: 30.1.1 - 30.1.4   2019.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Technical Digest - International Electron Devices Meeting, IEDM  

    We report homoepitaxial GaN p-n junction diodes with novel beveled-mesa structures. The n-layers and p-layers, the doping concentrations of which are comparable, were prepared. We found that electric field crowding does not occur in the structure using TCAD simulation. The fabricated devices showed the breakdown voltages of 180-480 V, small leakage currents, and excellent avalanche capabilities. The breakdown voltages increased at elevated temperature. At the breakdown, nearly uniform luminescence in the entire p-n junctions was observed in all the devices. These results are strong evidences that the uniform avalanche breakdowns occurred in the devices. We carefully characterized the depletion layer width at the breakdown, and the parallel-plane breakdown electric fields of 2.8-3.5 MV/cm were obtained, which are among the best of the reported non-punch-through GaN vertical devices.

    DOI: 10.1109/IEDM.2018.8614669

    Scopus

  8. Franz-Keldysh effect in 4H-SiC p-n junction diodes under high electric field along the 〈1120〉 direction

    Maeda T., Chi X., Tanaka H., Horita M., Suda J., Kimoto T.

    Japanese Journal of Applied Physics   Vol. 58 ( 9 )   2019

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Electric-field dependence of optical absorption induced by Franz-Keldysh (FK) effect strongly depends on the value of the reduced effective mass along electric field. In this study, reverse current-voltage characteristics of 4H-SiC{1120} p-n junction diodes under sub-bandgap illumination were investigated. Under a reverse bias condition, a photocurrent induced by FK effect was observed and increased with the reverse voltage. We calculated a photocurrent with consideration of phonon-assisted optical absorption induced by FK effect in a depletion region using the reduced effective mass perpendicular to the c-axis (μ⊥ = 0.26 m0), and the calculated values showed good agreement with the experimental values. This result indicates that the anisotropy of optical absorption induced by FK effect in 4H-SiC is small, since the reduced effective mass perpendicular to the c-axis (μ⊥ = 0.26 m0) is close to that parallel to the c-axis (μ∥ m = 0.28 m0).

    DOI: 10.7567/1347-4065/ab3873

    Scopus

  9. Shockley-Read-Hall lifetime in homoepitaxial p-GaN extracted from recombination current in GaN p-n<sup>+</sup> junction diodes

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    Japanese Journal of Applied Physics   Vol. 58 ( SC )   2019

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The Shockley-Read-Hall (SRH) lifetime in homoepitaxial p-GaN (N a = 1 × 1017 cm-3) is investigated by analyzing forward current-voltage (I-V) characteristics in GaN-on-GaN p-n+ junction diodes with mesa-isolation structure. The ideality factor around 2 due to recombination current was obtained in the 1.8-2.7 V window, which is different from the characteristic of a p+-n- junction involving considerable diffusion current. The recombination current was proportional to the junction area, indicating that the recombination current is a bulk component, not a mesa-surface component. Analyzing the recombination current with consideration of the SRH recombination rate in the depletion layer, we obtained an SRH lifetime of 46 ps at 298 K. The temperature dependence of the I-V characteristics was also investigated and the SRH lifetimes were extracted in the range of 223-573 K. The SRH lifetime in homoepitaxial p-GaN followed the empirical power law of = 1.2 × 10-16 × T 2.25 (s).

    DOI: 10.7567/1347-4065/ab07ad

    Scopus

  10. Determination of Surface Recombination Velocity From Current-Voltage Characteristics in SiC p-n Diodes

    Asada Satoshi, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 65 ( 11 ) page: 4786 - 4791   2018.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Surface recombination velocity on mesa sidewalls of SiC p-n diodes with various surface passivation conditions was evaluated from the device-size-dependent preexponential factor of recombination current (J0rec). The diodes passivated by SiO2 with postoxidation nitridation were dipped into HF to eliminate a shunt current, which is evoked by the nitrided SiO2 layer and disturbs the analysis of the recombination current. For accurate determination of the surface recombination velocity, an effective recombination zone width was precisely derived taking account of the distribution of carrier density in the depletion layer. The surface recombination velocity of the diodes without any passivation and with the postoxidation nitridation (NO annealing at 1250 °C for 70 min) was determined as 1.2 × 107 and 6.0 × 105 cm/s, respectively, which indicates that the postoxidation nitridation can reduce the surface recombination by a factor of about 20. We confirmed that TCAD simulation could reproduce the current-voltage characteristics by utilizing the extracted parameters. In addition, an evaluation method was proposed to determine the surface recombination velocity from the high-current region, where diffusion current is dominant.

    DOI: 10.1109/TED.2018.2867545

    Web of Science

    Scopus

  11. Carrier lifetime and breakdown phenomena in SiC power device material

    Kimoto T., Niwa H., Okuda T., Saito E., Zhao Y., Asada S., Suda J.

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   Vol. 51 ( 36 )   2018.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Physics D: Applied Physics  

    Recent progress and current understanding of carrier lifetimes and avalanche phenomena in silicon carbide (SiC) are reviewed. The acceptor level of carbon vacancy (V C), called the Z 1/2 center, has been identified to be the primary carrier lifetime killer in SiC. The V C defects can be eliminated by the introduction of excess carbon atoms followed by carbon diffusion in the bulk region. The true bulk lifetime after V C elimination was estimated to be approximately 110 μs. The doping dependence of carrier lifetimes in n- and p-type SiC is also presented. The impact ionization coefficients of electrons and holes were extracted in the temperature range of 298 to 423 K. The intrinsic critical electric field strength of SiC0 0 0 1 was determined to be 2.0, 2.5, and 3.3 MV cm-1 for doping densities of 1 × 1015, 1 × 1016, and 1 × 1017 cm-3, respectively, at room temperature; it slightly increased at elevated temperature. The obtained set of impact ionization coefficients has enabled us to accurately predict the breakdown voltage of SiC devices, including its temperature dependence. Due to the unusually low impact ionization coefficient of electrons, the breakdown voltage of a SiC p+n junction is about 6%-9% higher than that of an n+p junction with a given doping density.

    DOI: 10.1088/1361-6463/aad26a

    Web of Science

    Scopus

  12. Phonon-assisted optical absorption due to Franz-Keldysh effect in 4H-SiC p-n junction diode under high reverse bias voltage

    Maeda Takuya, Chi Xilun, Horita Masahiro, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 9 )   2018.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.7567/APEX.11.091302

    Web of Science

    Scopus

  13. Analytical formula for temperature dependence of resistivity in p-type 4H-SiC with wide-range doping concentrations

    Asada Satoshi, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 57 ( 8 )   2018.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Temperature dependence of resistivity from 250 to 900K in p-type 4H-SiC with various doping concentrations (5.8 × 1014-7.1 × 1018cm-3) was presented. The resistivity was obtained by the van der Pauw method in samples, whose doping concentrations were precisely determined in our previous work. From the experimental results, coefficients for a fitting formula with polynomial approximation were derived. We confirmed that the fitting formula can accurately estimate the resistivity of p-type SiC with wide-range doping concentrations.

    DOI: 10.7567/JJAP.57.088002

    Web of Science

    Scopus

  14. Accurate method for estimating hole trap concentration in n-type GaN via minority carrier transient spectroscopy

    Kanegae Kazutaka, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 7 )   2018.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.7567/APEX.11.071002

    Web of Science

    Scopus

  15. Characterization of carrier concentration and mobility of GaN bulk substrates by Raman scattering and infrared reflectance spectroscopies

    Kanegae Kazutaka, Kaneko Mitsuaki, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 57 ( 7 )   2018.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.7567/JJAP.57.070309

    Web of Science

    Scopus

  16. Impacts of Finger Numbers on ON-State Characteristics in Multifinger SiC BJTs With Low Base Spreading Resistance

    Asada Satoshi, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 65 ( 7 ) page: 2771 - 2777   2018.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Impacts of finger numbers on ON-state characteristics in multifinger 10-kV-class SiC bipolar junction transistors (BJTs), whose base spreading resistance is sufficiently reduced by using aluminum ion implantation, were investigated by performing TCAD simulations. Common-emitter current-voltage characteristics of the BJTs with different base current densities and carrier lifetimes in the collector layer were analyzed. The simulation results exhibited that the BJTs with fewer finger numbers could achieve superior characteristics owing to an expansion of a conductivity-modulated region and to a higher current density per finger. In addition, we showed that BJTs with a punchthrough structure have a potential to achieve superior characteristics suitable for power device applications under a certain condition, where strong conductivity modulation occurs. The presented results indicate that the appropriate finger numbers should be designed for a better performance of the multifinger SiC BJTs.

    DOI: 10.1109/TED.2018.2834354

    Web of Science

    Scopus

  17. Theoretical analysis of Hall factor and hole mobility in p-type 4H-SiC considering anisotropic valence band structure

    Tanaka H., Asada S., Kimoto T., Suda J.

    JOURNAL OF APPLIED PHYSICS   Vol. 123 ( 24 )   2018.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The temperature dependencies of hole density and hole mobility of p-type 4H-SiC obtained by Hall effect measurement were theoretically analyzed taking account of its anisotropic valence band structure. The experimental Hall factor, which was derived from the ratio of theoretical hole density to experimental Hall hole density, was reproduced by theoretical Hall factor computed using the valence band structure and relaxation times of scattering mechanisms. The product of the theoretical Hall factor and drift mobility computed by the same transport model agreed well with the experimental Hall mobility. Based on analyses of the results, it was revealed that the temperature dependence of Hall factor can be explained by considering the anisotropic valence band structure along with consideration of anisotropic relaxation times. The contribution of each scattering mechanism was also discussed, and empirical formulas for Hall and drift mobilities are presented.

    DOI: 10.1063/1.5025776

    Web of Science

    Scopus

  18. Franz-Keldysh effect in GaN p-n junction diode under high reverse bias voltage

    Maeda Takuya, Narita Tetsuo, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 112 ( 25 )   2018.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.5031215

    Web of Science

    Scopus

  19. A comparative study on electrical characteristics of 1-kV pnp and npn SiC bipolar junction transistors

    Okuda Takafumi, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 57 ( 4 )   2018.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.7567/JJAP.57.04FR04

    Web of Science

    Scopus

  20. Sources of carrier compensation in metalorganic vapor phase epitaxy-grown homoepitaxial n-type GaN layers with various doping concentrations

    Sawada Naoki, Narita Tetsuo, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 4 )   2018.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.7567/APEX.11.041001

    Web of Science

    Scopus

  21. Impacts of energy relaxation process on quasi-ballistic hole transport capability in germanium and silicon nanowires

    Tanaka H., Suda J., Kimoto T.

    JOURNAL OF APPLIED PHYSICS   Vol. 123 ( 2 )   2018.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The quasi-ballistic hole transport in germanium and silicon nanowires was theoretically investigated by solving the Boltzmann transport equation taking account of phonon scattering in an atomistic framework. Comparison of quasi-ballistic hole transport capabilities between germanium and silicon nanowires showed that the transmission coefficients for the two materials are similar. Then, the behavior of forward and backward current fluxes was analyzed focusing on the impact of energy relaxation process. The slower energy relaxation of holes in germanium nanowires leads to a longer distance where backscattering enables holes to return to the source. This cancels the benefit of the longer mean free path of holes in germanium nanowires, resulting in similar transmission coefficients in germanium and silicon nanowires.

    DOI: 10.1063/1.5010052

    Web of Science

    Scopus

  22. Deep-ultraviolet light emission from 4H-AlN/4H-GaN short-period superlattice grown on 4H-SiC(11(2)over-bar0)

    Kaneko M., Ueta S., Horita M., Kimoto T., Suda J.

    APPLIED PHYSICS LETTERS   Vol. 112 ( 1 )   2018.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    AlN/GaN short-period superlattices (SPSLs) were grown on 4H-SiC(112-0) substrates with a 4H-AlN template layer. The thickness of the GaN layers was controlled to be less than 1 nm to suppress the generation of extended defects. The stacking fault and threading dislocation density were found to be 3 × 105 cm-1 and 6 × 107 cm-2, respectively, which were as low as those for a 4H-AlN single layer. The superlattice replicated the polytype of the underlying 4H-AlN layer (4H-SiC substrate), meaning that a 4H-AlN/4H-GaN SPSL was grown. Roomerature cathodoluminescence measurements revealed that the 4H-AlN/4H-GaN SPSLs exhibited intense luminescence in the deep ultraviolet region of 4.4-5.0 eV, depending on the GaN layer thickness. The emission wavelengths of the SPSLs fairly agreed with the estimation based on the Kronig-Penney model.

    DOI: 10.1063/1.5006435

    Web of Science

    Scopus

  23. Effects of parasitic region in SiC bipolar junction transistors on forced current gain

    Asada S., Suda J., Kimoto T.

    Materials Science Forum   Vol. 924 MSF   page: 629 - 632   2018

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    Effects of a parasitic region in SiC BJTs on conductivity modulation and a forced current gain (βF) were investigated by using TCAD simulation with various device structures. By introducing an Al+-implanted region below the base parasitic region, βF can be improved because the implanted region can reduce the base spreading resistance, leading to alleviation of debiasing effect. βF in devices with various parasitic areas, whose base spreading resistances were reduced by the Al+-implantation, were compared. We found that βF can be enhanced by expanding the parasitic area if the base spreading resistance is sufficiently reduced. The higher βF is attributed to an expanded conductivity-modulated region. The collector current spreading in the collector layer and hole injection from the parasitic region as well as from the intrinsic region can play a role to evoke conductivity modulation. Thus, the larger parasitic region can expand the conductivity-modulated region, which results in expansion of an active area and the enhancement of βF, though a higher base voltage is required.

    DOI: 10.4028/www.scientific.net/MSF.924.629

    Scopus

  24. Theoretical analysis of quasi-ballistic hole transport in Ge and Si nanowires focusing on energy relaxation process

    Tanaka H., Suda J., Kimoto T.

    2017 Silicon Nanoelectronics Workshop, SNW 2017   Vol. 2017-January   page: 35 - 36   2017.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2017 Silicon Nanoelectronics Workshop, SNW 2017  

    The quasi-ballistic hole transport capabilities of Ge and Si NWs were calculated using atomistic electron-phonon coupling and Boltzmann transport equation. Analyzing the forward and backward current fluxes, it was shown that the positive impact of high mobility of Ge is canceled by its slower energy relaxation, which results in comparable transmission coefficients and current transport capabilities between Ge and Si NWs.

    DOI: 10.23919/SNW.2017.8242284

    Scopus

  25. Carrier Lifetimes in Lightly-Doped p-Type 4H-SiC Epitaxial Layers Enhanced by Post-growth Processes and Surface Passivation

    Okuda T., Miyazawa T., Tsuchida H., Kimoto T., Suda J.

    Journal of Electronic Materials   Vol. 46 ( 11 ) page: 6411 - 6417   2017.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Electronic Materials  

    We investigated limiting factors of carrier lifetimes and their enhancement by post-growth processes in lightly-doped p-type 4H-SiC epitaxial layers (NA ∼ 2 × 1014 cm−3). We focused on bulk recombination, surface recombination, and interface recombination at the epilayer/substrate, respectively. The carrier lifetime of 2.8 μs in an as-grown epilayer was improved to 10 μs by the combination of VC-elimination processes and hydrogen annealing. By employing surface passivation with deposited SiO2 followed by POCl3 annealing, a long carrier lifetime of 16 μs was obtained in an oxidized epilayer. By investigating carrier lifetimes in a self-standing p-type epilayer, it was revealed that the interface recombination at the epilayer/substrate was smaller than the surface recombination on a bare surface. We found that the VC-elimination process, hydrogen annealing, and surface passivation are all important for improving carrier lifetimes in lightly-doped p-type epilayers.

    DOI: 10.1007/s11664-017-5677-4

    Scopus

  26. Analysis of quasi-ballistic hole transport capability of Ge and Si nanowire pMOSFETs by a quantum-corrected Boltzmann transport equation

    Tanaka H., Suda J., Kimoto T.

    International Conference on Simulation of Semiconductor Processes and Devices, SISPAD   Vol. 2017-September   page: 277 - 280   2017.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:International Conference on Simulation of Semiconductor Processes and Devices, SISPAD  

    The quasi-ballistic hole transport capabilities of Ge and Si nanowire pMOSFETs were analyzed based on a quantum-corrected Boltzmann transport equation. A new formalism of quantum-correction potential was proposed, and using this model, the current drive capabilities of Ge and Si nanowire pMOSFETs were compared. Though the ON-current was larger in the Ge nanowire pMOSFET, the transmission coefficients are similar between Ge and Si, because the higher hole mobility of Ge is canceled by its slower energy relaxation. Thus, the larger current of the Ge nanowire pMOSFET was attributed to its larger injection current. The impact of device geometry on the performance was also investigated, and the [110]-oriented Ge nanowire pMOSFET with a 15 nm gate length exhibited the highest performance among the devices considered in this study.

    DOI: 10.23919/SISPAD.2017.8085318

    Scopus

  27. Correlation between shapes of Shockley stacking faults and structures of basal plane dislocations in 4H-SiC epilayers

    Iijima A., Kamata I., Tsuchida H., Suda J., Kimoto T.

    Philosophical Magazine   Vol. 97 ( 30 ) page: 2736 - 2752   2017.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Philosophical Magazine  

    Shockley-type stacking faults expanded in 4H–SiC epilayers induced by ultraviolet illumination were investigated using a photoluminescence imaging method, a photoluminescence mapping method and X-ray topography. After ultraviolet illumination, more than 30 patterns of Shockley-type stacking faults which expanded from perfect basal plane dislocations were observed by photoluminescence imaging. The initial basal plane dislocations were crystallographically classified, and individual shapes of expanded Shockley-type stacking faults were predicted. The correspondence between the predicted shapes and observed ones was discussed.

    DOI: 10.1080/14786435.2017.1350788

    Scopus

  28. Characterization of lightly-doped n- and p-type homoepitaxial GaN on free-standing substrates

    Horita M., Suda J.

    IMFEDK 2017 - 2017 International Meeting for Future of Electron Devices, Kansai     page: 86 - 87   2017.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IMFEDK 2017 - 2017 International Meeting for Future of Electron Devices, Kansai  

    Hall-effect measurements for n-type and p-type GaN with low doping concentration are presented. The GaN layers were grown by metal-organic vapor phase epitaxy on hydride-vapor-phase-epitaxy-grown free-standing GaN substrates. For n-GaN, the origin of acceptor which compensating donor is not only C but also native defects for the Si doping concentration of 1016 cm-3 level. The electron mobility is mainly limited by ionized impurity scattering or polar optical phonon scattering in the temperature less or higher than 200 K, respectively. For p-GaN, lightly Mg doping of mid 1016 cm-3 was achieved, which shows the donor concentration of 3.2×1016 cm-3 and the mobility of 31 cm2/Vs at 300 K.

    DOI: 10.1109/IMFEDK.2017.7998055

    Scopus

  29. Effect of Postoxidation Nitridation on Forward Current-Voltage Characteristics in 4H-SiC Mesa p-n Diodes Passivated With SiO2

    Asada Satoshi, Kimoto Tsunenobu, Suda Jun

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 64 ( 7 ) page: 3016 - 3018   2017.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    An origin of shunt current, a ledge in forward current-voltage ( ${I}$ - ${V}$ ) characteristics, in 4H-SiC mesa p-n diodes was investigated by adopting various surface passivation processes. Experimental results indicated that the shunt current path is located along the mesa sidewall and the shunt current is enlarged with increasing NO-annealing period and temperature. Based on these results, we qualitatively explain that nitrogen-related positive charges near the SiC/SiO2 interface, which are formed by postoxidation nitridation, induce band bending and lowering of the diffusion potential along the mesa sidewall, resulting in occurrence of the shunt current.

    DOI: 10.1109/TED.2017.2700336

    Web of Science

    Scopus

  30. Electrical properties of n- and p-type 4H-SiC formed by ion implantation into high-purity semi-insulating substrates

    Fujihara Hiroaki, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 56 ( 7 )   2017.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Phosphorus or aluminum ions were directly implanted into semi-insulating 4H-SiC substrates with no epitaxial layers to form n- or p-type layers, respectively, with doping densities in the range from 1017 to 1019 cm-3. The electrical properties of these implanted layers annealed at 1650°C were characterized by Hall effect measurements in the temperature range of 160-900K. The electrical activation ratios of implanted dopants were 88-98%. The density of compensating defects was higher in Al+-implanted layers than in P+-implanted ones. The mobilities of the implanted layers were mostly comparable to those of epitaxial layers in the doping range investigated.

    DOI: 10.7567/JJAP.56.070306

    Web of Science

    Scopus

  31. Design Criterion for SiC BJTs to Avoid ON-Characteristics Degradation Due to Base Spreading Resistance

    Asada Satoshi, Kimoto Tsunenobu, Suda Jun

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 64 ( 5 ) page: 2086 - 2091   2017.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    It is empirically known that the ON-resistance (voltage) of the SiC bipolar junction transistors (BJTs) with a thin-base layer is prone to be larger than the resistance of a voltage-blocking collector layer. In this paper, we explain the mechanism of this degradation of ON-characteristics by focusing on a high base spreading resistance and a parasitic diode existing below the base contact. An equivalent circuit model of the SiC BJT was proposed, and SPICE simulation was performed.In addition, TCAD simulation confirmed the validity of the model well. Based on the model, a design criterion to avoid the unwanted increase of the ON-resistance is proposed.

    DOI: 10.1109/TED.2017.2684181

    Web of Science

    Scopus

  32. Temperature dependence of barrier height in Ni/n-GaN Schottky barrier diode

    Maeda T., Okada M., Ueno M., Yamamoto Y., Kimoto T., Horita M., Suda J.

    Applied Physics Express   Vol. 10 ( 5 )   2017.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The temperature dependence of barrier height in a Ni/n-GaN Schottky barrier diode fabricated on a GaN homoepitaxial layer was investigated by capacitance-voltage, current-voltage, and internal photoemission measurements in the range of 223-573 K. The barrier height obtained by these methods linearly decreased with increasing temperature. The temperature coefficient was %(1.7-2.3) ' 10-4 eV/K, which is about half of the temperature coefficient of the band gap reported previously. This indicates that the decrease in the barrier height may mainly reflect the shrinkage of the band gap (lowering of the conduction band edge) in GaN with increasing temperature.

    DOI: 10.7567/APEX.10.051002

    Scopus

  33. Interface properties of NO-annealed 4H-SiC (0001), (11(2)over-bar0), and (1(1)over-bar00) MOS structures with heavily doped p-bodies

    Kobayashi Takuma, Nakazawa Seiya, Okuda Takafumi, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 121 ( 14 )   2017.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    We investigated electrical characteristics of nitric oxide (NO)-annealed silicon carbide (SiC) (0001 ), (11 2 ¯ 0 ), and (1 1 ¯ 00 ) metal-oxide-semiconductor field effect transistors (MOSFETs) with heavily doped p-bodies (NA = 1 × 1017-3 × 1018 cm−3). Regardless of crystal faces or off-direction, the channel mobility decreased for higher acceptor density. We evaluated the interface state density (Dit) very near the bottom edge of 2-dimensional density of states (2D-DOS) in the conduction band of SiC from the low-temperature subthreshold slope of the MOSFETs. When the acceptor density of the p-body of the MOSFET is increased, the energy levels of 2D-DOS increase due to a stronger quantum confinement effect. Accordingly, the carriers in the heavily doped channel are influenced by the interface states located at higher energy levels. In the SiC MOS structures, the Dit values significantly increase near the conduction band edge (EC). Thus, MOSFETs on heavily doped p-bodies are affected by the higher density of Dit, leading to substantially lower mobility.

    DOI: 10.1063/1.4981127

    Web of Science

    Scopus

  34. Reduction of interface state density in SiC (0001) MOS structures by post-oxidation Ar annealing at high temperature

    Kobayashi Takuma, Suda Jun, Kimoto Tsunenobu

    AIP ADVANCES   Vol. 7 ( 4 )   2017.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AIP Advances  

    We found that post-oxidation Ar annealing at high temperature is effective in reducing the interface state density (Dit) near the conduction band edge (EC) of SiC (0001) MOS structures. The Dit reduction effect is comparable to that of nitridation process (annealing in nitric oxide (NO)) which has been a standard in SiC MOS technologies, without introducing any foreign atoms into the interface/oxide. The generation of fast interface states, which have been pointed out as a problem of nitridation process, is suppressed in the case of Ar annealing. In the proposed method, the final Dit values are mainly determined by the Ar annealing temperature rather than the initial oxidation temperature. The Dit values are not sensitive to the cooling speed, which means that rapid cooling is not necessary in the proposed method.

    DOI: 10.1063/1.4980024

    Web of Science

    Scopus

  35. Ultrahigh-Voltage SiC MPS Diodes With Hybrid Unipolar/Bipolar Operation

    Niwa Hiroki, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 64 ( 3 ) page: 874 - 881   2017.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    In this paper, ultrahigh-voltage (UHV) SiC devices with hybrid unipolar/bipolar operation are introduced and demonstrated. As the first step of such a device, a merged p-i-n Schottky (MPS) diode with an epitaxial p+-anode layer is proposed to reduce the conduction loss of a bipolar device in the low current region. A 'snapback' phenomenon is intensively investigated by analytical modeling, device simulation, and experiment and a design guideline of snapback-free hybrid operating MPS diodes is presented. Using the design guideline, snapback-free MPS diodes are fabricated and forward characteristics are investigated. By using a proper edge termination structure, a UHV SiC MPS diode with breakdown voltage of 11.3 kV is demonstrated.

    DOI: 10.1109/TED.2016.2636573

    Web of Science

    Scopus

  36. Analysis of High-Field Hole Transport in Germanium and Silicon Nanowires Based on Boltzmann's Transport Equation

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON NANOTECHNOLOGY   Vol. 16 ( 1 ) page: 118 - 125   2017.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Nanotechnology  

    In this paper, high-field hole transport in germanium nanowires was studied by using Boltzmann's transport equation in an atomistic framework. The scattering mechanisms taken into account are phonon and surface roughness. The hole drift velocities of [110], [111], and [112]-oriented germanium nanowires showed negative-differential characteristics, while that of the [001] nanowire did not. The behavior of hole drift velocity was analyzed based on the highly nonparabolic and orientation-dependent valence band structure. High-field hole transport properties in silicon nanowires were also calculated, and the differences between germanium and silicon nanowires were discussed, focusing mainly on momentum and energy relaxation times. The [110], [111], and [112] silicon nanowires showed faster hole drift velocity at high field than the germanium nanowires with the same orientation. This was attributed to faster energy relaxation in silicon nanowires, which mitigates the negative differential mobility in silicon nanowires compared to germanium nanowires.

    DOI: 10.1109/TNANO.2016.2635110

    Web of Science

    Scopus

  37. Phonon frequencies of a highly strained AIN layer coherently grown on 6H-SiC (0001)

    Kaneko M., Kimoto T., Suda J.

    AIP ADVANCES   Vol. 7 ( 1 )   2017.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AIP Advances  

    Phonon frequencies of a high-quality AlN layer coherently grown on a 6H-SiC (0001) substrate are investigated by Raman scattering. Owing to the largest strain in our coherent AlN layer among heteroepitaxially grown AlN layers ever reported, phonon frequencies of the E2 (low), E2 (high), and A1 (LO) modes are considerably shifted to 244.5 (−3.3, compared with bulk AlN), 672.1 (+16.3), and 899 (+11)cm−1, respectively. Full widths at half maximum of the phonon modes in the coherent AlN are almost equal to those of high-quality bulk AlN, clearly indicating its high crystalline quality and uniform strain. We discuss accuracy of phonon deformation potentials reported by several other groups thorough comparing our experimental results.

    DOI: 10.1063/1.4974500

    Web of Science

    Scopus

  38. Characterization of lightly-doped n- and p-type homoepitaxial GaN on free-standing substrates

    Horita Masahiro, Suda Jun

    2017 IEEE INTERNATIONAL MEETING FOR FUTURE OF ELECTRON DEVICES, KANSAI (IMFEDK)     page: 86-87   2017

     More details

    Language:English   Publishing type:Research paper (scientific journal)  

    Web of Science

  39. Analysis of quasi-ballistic hole transport capability of Ge and Si nanowire pMOSFETs by a quantum-corrected Boltzmann transport equation

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    2017 INTERNATIONAL CONFERENCE ON SIMULATION OF SEMICONDUCTOR PROCESSES AND DEVICES (SISPAD 2017)     page: 277 - 280   2017

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  40. Insight into phonon scattering in Si nanowires through high-field hole transport: Impacts of boundary condition and comparison with bulk phonon approximation

    Tanaka H., Suda J., Kimoto T.

    33RD INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS   Vol. 864 ( 1 )   2017

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Physics: Conference Series  

    The impact of how to model phonon scattering on hole transport in Si nanowires was studied based on Boltzmann's transport equation. Boundary conditions for atomistic description of phonons in nanowires and approximation by bulk acoustic and optical phonons were analyzed in terms of their impacts on high-field hole transport. The boundary conditions for phonons influence the drift velocity and momentum relaxation time, especially at low electric field, but the energy relaxation time hardly depends on the boundary conditions. The impacts by the change of boundary conditions can be approximated by the change of the strength of acoustic phonon scattering in bulk phonon picture, though the behavior of energy relaxation and distribution function of holes can not be reproduced by bulk phonon approximation.

    DOI: 10.1088/1742-6596/864/1/012046

    Web of Science

    Scopus

  41. Theoretical Analysis of Quasi-ballistic Hole Transport in Ge and Si Nanowires Focusing on Energy Relaxation Process

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    2017 SILICON NANOELECTRONICS WORKSHOP (SNW)     page: 35 - 36   2017

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  42. Impact of annealing temperature on surface passivation of SiC epitaxial layers with deposited SiO<inf>2</inf> followed by POCl<inf>3</inf> annealing

    Okuda T., Kobayashi T., Kimoto T., Suda J.

    WiPDA 2016 - 4th IEEE Workshop on Wide Bandgap Power Devices and Applications     page: 233 - 235   2016.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:WiPDA 2016 - 4th IEEE Workshop on Wide Bandgap Power Devices and Applications  

    We investigate an impact of annealing temperature on surface passivation of SiC epitaxial layers with deposited SiO2 followed by POCl3 annealing. The POCl3 annealing process consists of two steps: (i) thermal annealing in POCl3 and (ii) subsequent thermal annealing in pure N2. We find that the annealing temperature of the subsequent N2 annealing is important to reduce surface recombination on SiC. For surface passivation, N2 annealing at high temperature at 1000° C is necessary.

    DOI: 10.1109/WiPDA.2016.7799944

    Scopus

  43. Control of carbon vacancy in SiC toward ultrahigh-voltage power devices

    Kimoto T., Kawahara K., Zippelius B., Saito E., Suda J.

    SUPERLATTICES AND MICROSTRUCTURES   Vol. 99   page: 151 - 157   2016.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Superlattices and Microstructures  

    A carbon vacancy defect is one of the most abundant point defects in SiC (as-grown, irradiated, annealed) and of technological importance because the acceptor-like level of a carbon monovacancy (Z1/2 center: EC – 0.63 eV) works as the primary carrier-lifetime killer in 4H–SiC. The carbon vacancy defects can be preferentially generated by either low-energy electron irradiation or high-temperature treatment in an inert gas ambient. On the other hand, the carbon vacancy defects can be almost eliminated by either a carbon-ion implantation process or thermal oxidation. By combination of these techniques, the density of carbon vacancy defects can be controlled in the wide range from 1011 cm−3 to 1015 cm−3 or even higher.

    DOI: 10.1016/j.spmi.2016.03.029

    Web of Science

    Scopus

  44. Promise and Challenges of High-Voltage SiC Bipolar Power Devices

    Kimoto Tsunenobu, Yamada Kyosuke, Niwa Hiroki, Suda Jun

    ENERGIES   Vol. 9 ( 11 )   2016.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Energies  

    Although various silicon carbide (SiC) power devices with very high blocking voltages over 10 kV have been demonstrated, basic issues associated with the device operation are still not well understood. In this paper, the promise and limitations of high-voltage SiC bipolar devices are presented, taking account of the injection-level dependence of carrier lifetimes. It is shown that the major limitation of SiC bipolar devices originates from band-to-band recombination, which becomes significant at a high-injection level. A trial of unipolar/bipolar hybrid operation to reduce power loss is introduced, and an 11 kV SiC hybrid (merged pin-Schottky) diodes is experimentally demonstrated. The fabricated diodes with an epitaxial anode exhibit much better forward characteristics than diodes with an implanted anode. The temperature dependence of forward characteristics is discussed.

    DOI: 10.3390/en9110908

    Web of Science

    Scopus

  45. Erratum: Franz-Keldysh effect in n-type GaN Schottky barrier diode under high reverse bias voltage (Appl. Phys. Express (2016) 9 (091002))

    Maeda T., Okada M., Ueno M., Yamamoto Y., Horita M., Suda J.

    Applied Physics Express   Vol. 9 ( 10 )   2016.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The reduced effective masses (μhh-e and μlh-e) were incorrect in the original manuscript. Table I and Fig. 4 should be replaced with the table and the figure shown below. The description "using a reduced effective mass of 0.14m0, which is calculated from the masses reported for electrons and holes in GaN" in line 44, column 1, page 1 should be replaced with "using the effective masses reported for electrons and holes in GaN, which are listed in Table I", and "a reduced effective mass of GaN (μ∥ = 0.14m0) was used" in line 34, column 2, page 3 should be replaced with "calculation was done by the two-band-model using the effective masses listed in Table I". The calculations of the absorption coefficient and the photocurrent was done by the two-hole-band-model using me, mhh, and mlh. The correction does not affect the results and conclusions in this paper.

    DOI: 10.7567/APEX.9.109201

    Scopus

  46. Theoretical analysis of high-field hole transport in germanium and silicon nanowires

    Tanaka H., Suda J., Kimoto T.

    2016 IEEE Silicon Nanoelectronics Workshop, SNW 2016     page: 192 - 193   2016.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2016 IEEE Silicon Nanoelectronics Workshop, SNW 2016  

    High-field hole transport in Ge nanowires was studied using Boltzmann's transport equation. The behavior of drift velocity was analyzed based on the highly non-parabolic valence band structure. High-field hole transport properties in Si nanowires were also calculated, and the differences between Ge and Si nanowires were discussed.

    DOI: 10.1109/SNW.2016.7578046

    Scopus

  47. Analysis of ballistic and quasi-ballistic hole transport properties in germanium nanowires based on an extended "Top of the Barrier" model

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    SOLID-STATE ELECTRONICS   Vol. 123   page: 143 - 149   2016.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Solid-State Electronics  

    The ballistic hole transport properties in rectangular cross-sectional germanium nanowire transistors with various geometries were studied based on the “Top of the Barrier” model. Then, by an extension of this model, the quasi-ballistic hole transport was discussed taking into account phonon and surface roughness scattering in the channel and source-to-drain direct tunneling. Among several nanowire geometries targeted in this study, the [1 1 0]-oriented nanowire with large height along [11¯0] ([1 1 0]/(1 1¯ 0) NW) exhibited the largest ballistic current. This was understood from its large density of states and resulting high hole density. Large density of states, however, enhances backscattering in the channel. An approximation analysis of quasi-ballistic transport suggested that the [1 1 0]/(0 0 1) NW with higher mobility can outperform [1 1 0]/(1 1¯ 0) NW when scattering and tunneling are considered.

    DOI: 10.1016/j.sse.2016.04.015

    Web of Science

    Scopus

  48. Franz-Keldysh effect in n-type GaN Schottky barrier diode under high reverse bias voltage

    Maeda T., Okada M., Ueno M., Yamamoto Y., Horita M., Suda J.

    Applied Physics Express   Vol. 9 ( 9 )   2016.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The photocurrent of GaN vertical Schottky barrier diodes was investigated under sub-bandgap wavelength light irradiation. Under a low reverse bias voltage, the photocurrent is induced by internal photoemission, while under a high reverse bias voltage, the photocurrent increases significantly with the bias voltage. This is due to sub-bandgap optical absorption in a depletion region due to the Franz-Keldysh effect. The voltage and wavelength dependences of the photocurrent are successfully explained quantitatively.

    DOI: 10.7567/APEX.9.091002

    Scopus

  49. SiC and GaN from the viewpoint of vertical power devices

    Suda J.

    Device Research Conference - Conference Digest, DRC   Vol. 2016-August   2016.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Device Research Conference - Conference Digest, DRC  

    Wide-bandgap (WBG) semiconductors have attracted great attention as materials for the next-generation power devices since they have superior material properties compared to silicon (Si). The most advanced WBG semiconductor for power devices is silicon carbide (SiC). In 1987, the growth technology called 'step-controlled epitaxy', which enables single-phase (polytype) growth, was developed. In 1993-1994, SiC Schottky-barrier diodes (SBDs) which exceeds the Si material limit was demonstrated. In 2001, SiC SBDs were commercialized. Key technologies for SiC SBDs were edge termination to obtain an ideal breakdown voltage and a junction barrier Schottky (JBS) structure to suppress reverse leakage current. For power MOSFETs, it took longer time due to low channel mobility at SiO2/SiC and oxide reliability issues. Channel mobility was much improved by post-oxidation nitridation in NO or N2O ambient. Now, channel mobility and reliability are well controlled (balanced). SiC power MOSFETs as well as power modules with SiC MOSFETs and SiC SBDs, are commercially available. Last 5 years, the implementation of SiC devices into electronic vehicles and railway trains were extensively investigated, demonstrating a significant improvement of power efficiency.

    DOI: 10.1109/DRC.2016.7548292

    Scopus

  50. Characterization of n-type and p-type GaN layers grown on free-standing GaN substrates

    Suda J., Horita M.

    2016 Compound Semiconductor Week, CSW 2016 - Includes 28th International Conference on Indium Phosphide and Related Materials, IPRM and 43rd International Symposium on Compound Semiconductors, ISCS 2016     2016.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2016 Compound Semiconductor Week, CSW 2016 - Includes 28th International Conference on Indium Phosphide and Related Materials, IPRM and 43rd International Symposium on Compound Semiconductors, ISCS 2016  

    Electrical characterization of low-doped n-type and p-type GaN layers grown by metal-organic vapor phase epitaxy are presented. The GaN layers were grown on hydride-vapor-phase-epitaxy-grown free-standing GaN substrates. For n-type GaN, the impact of electron trap on electrical characterization is discussed. Charging of trap in a depletion layer affects C-V characteristics. Correction is needed for depth profiling of net donor concentration. For p-type GaN, hole mobility for various Mg doping concentrations at various temperatures are presented. At 300 K, 33 cm2/Vs is obtained for p-type GaN with Mg doping concentration of mid 1016 cm-3.

    DOI: 10.1109/ICIPRM.2016.7528835

    Scopus

  51. Ion implantation technology in SiC for high-voltage/high-temperature devices

    Kimoto T., Kawahara K., Kaji N., Fujihara H., Suda J.

    2016 16th International Workshop on Junction Technology, IWJT 2016     page: 54 - 58   2016.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2016 16th International Workshop on Junction Technology, IWJT 2016  

    Electrical activation of implanted dopants and defect generation in SiC have been investigated. A nearly perfect (> 95%) electrical activation can be obtained including the implant tail region after annealing at 1650-1700 °C. The majority of point defects generated in implanted SiC can remarkably be reduced by thermal oxidation. The high activation ratio of implanted Al acceptors is a key factor for fabricating effective junction termination structures in high-voltage SiC devices. Recent high-quality semi-insulating SiC wafers offer the opportunity of high-temperature SiC integrated devices, which can be fabricated by only ion implantation without an epitaxial growth process.

    DOI: 10.1109/IWJT.2016.7486673

    Scopus

  52. Control of carrier lifetime of thick n-type 4H-SiC epilayers by high-temperature Ar annealing

    Saito Eiji, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 6 )   2016.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We investigated the carrier lifetime and Z1/2 center density of thick n-type 4H-SiC epilayers, which were oxidized and subsequently annealed in Ar at high temperatures. The Z1/2 center density decreased below the detection limit in the region to, at least, a 130μm depth by thermal oxidation. After subsequent high-temperature annealing, the Z1/2 center density increased with increasing annealing temperature, while the distribution of the Z1/2 center density was nearly uniform to a 130μm depth. The carrier lifetime could be controlled from 26 to 2.4 μs by changing the annealing temperature from 1600 to 1800 °C.

    DOI: 10.7567/APEX.9.061303

    Web of Science

    Scopus

  53. Hall-effect measurements of metalorganic vapor-phase epitaxy-grown p-type homoepitaxial GaN layers with various Mg concentrations

    Horita M., Takashima S., Tanaka R., Matsuyama H., Ueno K., Edo M., Suda J.

    Japanese Journal of Applied Physics   Vol. 55 ( 5 )   2016.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Mg-doped p-type gallium nitride (GaN) layers with doping concentrations in the range from 6.5 × 1016cm-3 (lightly doped) to 3.8 × 1019cm-3 (heavily doped) were investigated by Hall-effect measurement for the analysis of hole concentration and mobility. p-GaN was homoepitaxially grown on a GaN free-standing substrate by metalorganic vapor-phase epitaxy. The threading dislocation density of the p-GaN was 4 × 106cm-2 measured by cathodoluminescence mapping. Hall-effect measurements of p-GaN were carried out at a temperature in the range from 160 to 450 K. A low compensation ratio of less than 1-was revealed. We also obtained the depth of the Mg acceptor level of 235 meV considering the lowering effect by the Coulomb potential of ionized acceptors. The hole mobilities of 33 cm2V-1 s-1 at 300K and 72cm2V-1 s-1 at 200K were observed in lightly doped p-GaN.

    DOI: 10.7567/JJAP.55.05FH03

    Scopus

  54. Strain control in AlN top layer by inserting an ultrathin GaN interlayer on an AlN template coherently grown on SiC(0001) by PAMBE

    Kaneko Mitsuaki, Kimoto Tsunenobu, Suda Jun

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   Vol. 253 ( 5 ) page: 814 - 818   2016.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (B) Basic Research  

    Abstractauthoren We propose partially relaxed ultrathin GaN interlayer for strain control of AlN on SiC substrates. According to the degree of relaxation of the GaN interlayer, the lattice constant of the interlayer changes from that of SiC to that of bulk GaN, which leads to strain control of an AlN top layer grown on the interlayer. Growth of these layers is conducted by plasma-assisted molecular beam epitaxy. Before growing the interlayer, an AlN layer coherently grown on SiC is used as a template layer. The interlayers that have different degrees of relaxation are successfully obtained by changing the interlayer thickness. As a result, strain values of the AlN top layer grown on the interlayers are widely controlled from compressive (-0.53%) to tensile (+ 0.07%). TEM observation revealed the relaxation is induced by U-shaped half-loop dislocations originating from the GaN interlayer.

    DOI: 10.1002/pssb.201552649

    Web of Science

    Scopus

  55. Surface passivation on 4H-SiC epitaxial layers by SiO2 with POCl3 annealing

    Okuda Takafumi, Kobayashi Takuma, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 5 )   2016.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We investigated surface passivation on 4H-SiC epitaxial layers with deposited or thermally grown SiO2 followed by POCl3 annealing. The measured carrier lifetime in a p-type epilayer with deposited SiO2 was limited to 0.5 μs and it was improved to 3.0 μs after POCl3 annealing. In an n-type epilayer, a measured carrier lifetime of 5.8 μs was improved to 12 μs after POCl3 annealing. We found a clear relationship between the measured carrier lifetime and the interface state density at SiO2/n-SiC after POCl3 annealing, suggesting that the reduction in interface state density lowered the surface recombination velocity on the 4H-SiC.

    DOI: 10.7567/APEX.9.051301

    Web of Science

    Scopus

  56. Interface state density of SiO2/p-type 4H-SiC (0001), (11(2)over-bar0), (1(1)over-bar00) metal-oxide-semiconductor structures characterized by low-temperature subthreshold slopes

    Kobayashi Takuma, Nakazawa Seiya, Okuda Takafumi, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS LETTERS   Vol. 108 ( 15 )   2016.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    Interface properties of heavily Al-doped 4H-SiC (0001) (Si-face), (1120) (a-face), and (1100) (m-face) metal-oxide-semiconductor (MOS) structures were characterized from the low-temperature gate characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs). From low-temperature subthreshold slopes, interface state density (Dit) at very shallow energy levels (ET) near the conduction band edge (Ec) was evaluated. We discovered that the Dit near Ec (Ec - 0.01 eV < ET < Ec) increases in MOS structures with higher Al doping density for every crystal face (Si-, a-, and m-face). Linear correlation is observed between the channel mobility and Dit near Ec, and we concluded that the mobility drop observed in heavily doped MOSFETs is mainly caused by the increase of Dit near Ec.

    DOI: 10.1063/1.4946863

    Web of Science

    Scopus

  57. Modeling of surface roughness scattering in nanowires based on atomistic wave function: Application to hole mobility in rectangular germanium nanowires

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    PHYSICAL REVIEW B   Vol. 93 ( 15 )   2016.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physical Review B  

    The authors present a calculation model of surface roughness scattering (SRS) in nanowires (NWs) based on atomistic description of electronic states by an sp3d5s∗ tight-binding scheme, and then this model is applied to hole transport in rectangular cross-sectional germanium (Ge) NWs. In this SRS model, the change of electronic band structures due to width or height reduction is first computed, and then it is expressed using an equivalent potential near the surface. The perturbation corresponding to a surface roughness is calculated from this equivalent potential. Using the aforementioned SRS model, hole mobility in Ge NWs was computed taking into account phonon scattering and SRS. The impacts of SRS on hole mobility in Ge NWs were analyzed, focusing on the valence band structure and hole states of NWs. The main results are as follows. At low hole density, the impacts of SRS are strongly dependent on NW geometry, and Ge NWs with high phonon-limited hole mobility, such as rectangular cross-sectional [110]-oriented NWs with large height along the [001] direction and square cross-sectional [111]-oriented NWs, tend to be less affected by SRS. At high hole density, however, the geometry dependence of hole mobility becomes weaker. These are understood from the nature of hole states and the valence band structure.

    DOI: 10.1103/PhysRevB.93.155303

    Web of Science

    Scopus

  58. Hall scattering factors in p-type 4H-SiC with various doping concentrations

    Asada Satoshi, Okuda Takafumi, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 4 )   2016.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The Hall scattering factor (γH) in p-type 4H-SiC with various aluminum doping concentrations of 5.8 ' 1014-7.1 ' 1018cm%3 was investigated from 300 to 900 K. γH was determined by comparing the Hall coefficient with the theoretical carrier concentration derived from acceptor and donor concentrations obtained from secondary ion mab spectrometry and capacitance-voltage measurements. γH decreased with increasing temperature or doping concentration; γH = 1-0.4 for the doping concentration of 5.8 ' 1014cm%3 and γH = 0.5-0.2 for the doping concentration of 7.1 ' 1018cm%3. The dependence might be caused by the anisotropic and nonparabolic valence band structure of 4H-SiC.

    DOI: 10.7567/APEX.9.041301

    Web of Science

    Scopus

  59. Special issue on wide-bandgap semiconductor power electronics Preface

    Suda Jun

    SEMICONDUCTOR SCIENCE AND TECHNOLOGY   Vol. 31 ( 3 )   2016.3

     More details

    Publishing type:Research paper (scientific journal)   Publisher:Semiconductor Science and Technology  

    DOI: 10.1088/0268-1242/31/3/030301

    Web of Science

    Scopus

  60. Strong impact of the initial III/V ratio on the crystalline quality of an AlN layer grown by rf-plasma-assisted molecular-beam epitaxy

    Kaneko Mitsuaki, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 9 ( 2 )   2016.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The initial Al/N ratio for AlN growth of plasma-assisted molecular-beam epitaxy without plasma stabilization is investigated. The in situ growth rate of AlN gradually increased and its temporal variation corresponded to that of nitrogen atoms, which indicated that the initial Al/N ratio was excessively Al-rich. For AlN growth, such a high-Al/N-ratio condition resulted in a three-dimensional growth mode in the initial stage of the growth, and AlN with high threading dislocation density was obtained. By controlling the initial Al/N ratio by introducing a short standby time, the resulting two-dimensional initial growth mode leads to high-quality growth of AlN.

    DOI: 10.7567/APEX.9.025502

    Web of Science

    Scopus

  61. Characterization of N-Type and P-Type GaN Layers Grown on Free-Standing GaN Substrates

    Suda Jun, Horita Masahiro

    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS)     2016

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  62. ESR study on hydrogen passivation of intrinsic defects in p-type and semi-insulating 4H-SiC

    Murakami K., Tanai S., Okuda T., Suda J., Kimoto T., Umeda T.

    Materials Science Forum   Vol. 858   page: 318 - 321   2016

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    We studied the hydrogen passivation/depassivation of four types of intrinsic defects (EI5/6, HEI7/8, HEI9/10, and P6/7) in p-type and semi-insulating 4H-SiC by means of electron spin resonance (ESR) for examining the origin of carrier-lifetime-killing defects. We suggest that the HEI7/8 and P6/7 centers are the strongest candidate for the origin of the lifetime-killing defects.

    DOI: 10.4028/www.scientific.net/MSF.858.318

    Scopus

  63. Impact of Annealing Temperature on Surface Passivation of SiC Epitaxial Layers with Deposited SiO2 Followed by POCl3 Annealing

    Okuda Takafumi, Kobayashi Takuma, Kimoto Tsunenobu, Suda Jun

    2016 IEEE 4TH WORKSHOP ON WIDE BANDGAP POWER DEVICES AND APPLICATIONS (WIPDA)     page: 233 - 235   2016

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  64. SiC and GaN from the Viewpoint of Vertical Power Devices

    Suda Jun

    2016 74TH ANNUAL DEVICE RESEARCH CONFERENCE (DRC)     2016

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  65. Theoretical Analysis of High-field Hole Transport in Germanium and Silicon Nanowires

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    2016 IEEE SILICON NANOELECTRONICS WORKSHOP (SNW)     page: 192 - 193   2016

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  66. Orientation and size effects on phonon-limited hole mobility in rectangular cross-sectional germanium nanowires

    Tanaka H., Mori S., Morioka N., Suda J., Kimoto T.

    2014 Silicon Nanoelectronics Workshop, SNW 2014     2015.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2014 Silicon Nanoelectronics Workshop, SNW 2014  

    The phonon-limited hole mobility in rectangular cross-sectional [001], [110], [111], and [112]-oriented germanium nanowires was calculated and the hole transport characteristics were compared. The calculation revealed that [110] germanium nanowires with larger height along [001] show high hole mobility and are favorable for p-channel FETs.

    DOI: 10.1109/SNW.2014.7348616

    Scopus

  67. Oxidation-induced majority and minority carrier traps in n- and p-type 4H-SiC

    Okuda Takafumi, Alfieri Giovanni, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 8 ( 11 )   2015.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We investigated majority and minority carrier traps in lightly doped n-and p-type 4H-SiC epitaxial layers before and after thermal oxidation using deep level transient spectroscopy and minority carrier transient spectroscopy. We detected oxidation-induced new minority carrier traps, HO1 (EV + 0.36 eV) and HO2 (EV + 0.54 eV) for n-type 4H-SiC, and EO1 (EC % 0.59 eV) and EO2 (EC % 0.84 eV) for p-type 4H-SiC after thermal oxidation at 1300 °C. After subsequent Ar annealing at 1550 °C, the HO1, HO2, and EO1 centers disappeared, whereas the concentration of the EO2 center increased. The properties of these carrier traps are discussed.

    DOI: 10.7567/APEX.8.111301

    Web of Science

    Scopus

  68. Impact Ionization Coefficients in 4H-SiC Toward Ultrahigh-Voltage Power Devices

    Niwa Hiroki, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 62 ( 10 ) page: 3326 - 3333   2015.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    A temperature dependence of impact ionization coefficients in 4H-SiC was studied in a wide range of electric field toward the accurate designing of ultrahigh-voltage devices. The photomultiplication measurement was conducted for various photodiodes with different multiplication layer structures to obtain multiplication factors and ionization coefficients in a wide range of electric field strength. Especially, using multiplication layer structure with low doping concentration, the hole impact ionization coefficient was extracted at low electric field of 1 MV/cm. In high-temperature measurement, the hole ionization coefficient decreased with the increase of temperature, as observed in other semiconductor materials. For the electron ionization coefficient, however, its temperature dependence was very small and values obtained at room temperature could be used, at least up to 150 °C.

    DOI: 10.1109/TED.2015.2466445

    Web of Science

    Scopus

  69. Impacts of surface roughness scattering on hole mobility in germanium nanowires

    Tanaka H., Suda J., Kimoto T.

    2015 Silicon Nanoelectronics Workshop, SNW 2015     2015.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2015 Silicon Nanoelectronics Workshop, SNW 2015  

    The hole mobility in rectangular cross-sectional germanium nanowires was calculated taking into account phonon and surface roughness scattering (SRS). SRS was modeled based on atomistic description of electronic states, and the impacts of SRS on hole mobility were analyzed.

    Scopus

  70. Temperature dependence of forward characteristics for ultrahigh-voltage SiC p-i-n diodes with a long carrier lifetime

    Kaji Naoki, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 54 ( 9 )   2015.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Forward characteristics of ultrahigh-voltage 4H-SiC p-i-n diodes having four different n<sup>-</sup>-layer (i-layer) thicknesses from 48 to 198μm were investigated in the temperature range from room temperature to 573 K. After enhancement of carrier lifetimes in i-layers, nearly ideal forward characteristics (differential on-resistance = 1.1-5.5mΩcm<sup>2</sup> at 100A/cm<sup>2</sup>) were obtained at room temperature. The forward voltage drop decreased with temperature, which is consistent with the temperature dependence of junction voltage. The differential on-resistance exhibited a slight increase at elevated temperatures, which can mainly be ascribed to the increase in substrate resistance.

    DOI: 10.7567/JJAP.54.098004

    Web of Science

    Scopus

  71. Impacts of orientation and cross-sectional shape on hole mobility of Si nanowire MOSFETs

    Fujihara H., Morioka N., Tanaka H., Suda J., Kimoto T.

    IMFEDK 2015 - 2015 International Meeting for Future of Electron Devices, Kansai     page: 106 - 107   2015.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IMFEDK 2015 - 2015 International Meeting for Future of Electron Devices, Kansai  

    We fabricated 〈100〉, 〈110〉, 〈111〉, and 〈112〉 p-channel gate-all-around Si nanowire (SiNW) MOSFETs, cross sections of which are rectangles with various widths, and investigated the hole mobility of the SiNW MOSFETs using the double Lm method. Measured hole mobilities of SiNW MOSFETs were about 80-140 cm2/Vs at surface carrier density of 1 × 1013 cm-2. The dependences of the hole mobility on orientations and cross-sectional shapes of nanowires were analyzed. The orientation and geometry dependences can be explained by the band structures calculated by tight-binding approximation.

    DOI: 10.1109/IMFEDK.2015.7158572

    Scopus

  72. Temperature dependence of current gain in 4H-SiC bipolar junction transistors

    Asada Satoshi, Okuda Takafumi, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 54 ( 4 )   2015.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The temperature dependence of current gain from 140 to 460K in 4H-SiC bipolar junction transistors (SiC BJTs) was investigated. The current gain increased from 110 to 1200 with decreasing temperature from 460 to 200 K. The high current gain at the low temperature can be ascribed to the enhanced incomplete ionization of aluminum acceptors in the base layer, resulting in the increase in injection efficiency. However, when the temperature was further reduced from 200 to 140 K, the current gain decreased from 1200 to 515, which is caused by high injection condition in the base layer, because of a very low hole concentration below 200 K.

    DOI: 10.7567/JJAP.54.04DP13

    Web of Science

    Scopus

  73. Progress in ultrahigh-voltage SiC devices for future power infrastructure

    Kimoto T., Suda J., Yonezawa Y., Asano K., Fukuda K., Okumura H.

    Technical Digest - International Electron Devices Meeting, IEDM   Vol. 2015-February ( February ) page: 2.5.1 - 2.5.4   2015.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Technical Digest - International Electron Devices Meeting, IEDM  

    UHV (> 15 kV) SiC PiN diodes and IGBTs with improved on-state performance are presented. Through enhancement of carrier lifetime and optimization of junction termination, a breakdown voltage over 26.9 kV and a differential on-resistance of 9.7 mΩcm2 were achieved for PiN diodes. Flip-type n-channel IGBTs with a chip size of 8 mm × 8 mm exhibited a breakdown voltage over 16 kV, and 6.5 kV - 60 A switching at 250°C was demonstrated.

    DOI: 10.1109/IEDM.2014.7046967

    Scopus

  74. Interface properties of 4H-SiC (1120) and 1100) MOS structures annealed in NO

    Nakazawa S., Okuda T., Suda J., Nakamura T., Kimoto T.

    IEEE Transactions on Electron Devices   Vol. 62 ( 2 ) page: 309 - 315   2015.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Interface properties of 4H-SiC (1120) and (1100) metal-oxide-semiconductor (MOS) structures annealed in nitric oxide are characterized by conductance, high-low, and C-Ψs methods. Compared with 4H-SiC (0001) MOS structures, generation of very fast interface states by nitridation is much smaller in 4H-SiC (1120) and (1100). The effective mobility of planar MOSFETs fabricated on Al+-implanted p-body doped to 1×1017 cm-3 is 103 cm2/Vs on (1100), 92 cm2/Vs on (1120), and 20 cm2/Vs on (0001). The mobility-limiting factors are discussed on the basis of experimental results. The high channel mobilities for (1120) and (1100) MOSFETs can be correlated with the lower density of fast interface states generated by nitridation.

    DOI: 10.1109/TED.2014.2352117

    Scopus

  75. Ultrahigh- Voltage SiC p-i-n Diodes With Improved Forward Characteristics

    Kaji Naoki, Niwa Hiroki, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 62 ( 2 ) page: 374 - 381   2015.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Silicon carbide (SiC) p-i-n diodes having five different n--layer ( i-layer) thicknesses from 48 to 268 μm are fabricated. The forward characteristics of SiC p-i-n diodes are significantly improved by carrier-lifetime enhancement. After this improvement, the differential on-resistance is inversely proportional to the square root of current density for all the diodes with different thicknesses of n--layer. As a result, the forward current density-voltage characteristics can be approximately expressed by a parabolic function, as in the case of Si p-i-n diodes. Using a 268- μm-thick n--layer, the lifetime enhancement, and an improved space-modulated junction termination extension structure, a very high blocking voltage over 26.9 kV and low differential on-resistance of 9.7 mΩ·cm2 are achieved.

    DOI: 10.1109/TED.2014.2352279

    Web of Science

    Scopus

  76. High-temperature operation of electrostatically-excited single-crystalline 4H-SiC microcantilever resonators

    Sato K., Adachi K., Okamoto H., Yamaguchi H., Kimoto T., Suda J.

    Materials Science Forum   Vol. 821-823   page: 914 - 918   2015

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    We fabricated electrostatically-excited single-crystalline 4H-SiC microcantilever resonators with various thicknesses and lengths. Their resonant characteristics were investigated from room temperature (RT) up to 600°C. The resonant frequency of the cantilevers decreased with increasing temperature. From the results, the temperature dependence of Young’s modulus of single-crystalline 4H-SiC was obtained, i.e., 3% decrement with increasing temperature from RT to 600°C. The cantilevers with different thicknesses showed different temperature dependences of the quality factor. A 2-μm-thick cantilever exhibited a high quality factor (Q) (250,000) at RT and the Q decreased to 6,000 at 600°C, which can be explained by thermoelastic damping. On the other hand, a Q of a 0.45-μm-thick cantilever was still high (50,000) even at 600°C.

    DOI: 10.4028/www.scientific.net/MSF.821-823.914

    Scopus

  77. Impacts of Orientation and Cross-sectional Shape on Hole Mobility of Si Nanowire MOSFETs

    Fujihara Hiroaki, Morioka Naoya, Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    2015 IEEE INTERNATIONAL MEETING FOR FUTURE OF ELECTRON DEVICES, KANSAI (IMFEDK)     2015

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  78. Influence of conduction-type on thermal oxidation rate in SiC(0001) with various doping densities

    Kobayashi T., Suda J., Kimoto T.

    Materials Science Forum   Vol. 821-823   page: 456 - 459   2015

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    It was discovered that the oxidation rate for SiC depended on the conduction type. The oxidation was performed for SiC(0001) with nitrogen doping (n-type) in the range from 2×1016 cm-3 to 1×1019 cm-3, and aluminum doping (p-type) in the range from 2×1015 cm-3 to 1×1019 cm-3, exhibiting a clear dependence. For n-type SiC the oxide thickness increases for higher doping density, and for p-type the thickness decreases. Note that in the case of Si oxidation, there exists very little difference of oxidation rate between the conduction types in such low doping density, and the dependence is peculiar to SiC.

    DOI: 10.4028/www.scientific.net/MSF.821-823.456

    Scopus

  79. Impacts of Surface Roughness Scattering on Hole Mobility in Germanium Nanowires

    Tanaka Hajime, Suda Jun, Kimoto Tsunenobu

    2015 SILICON NANOELECTRONICS WORKSHOP (SNW)     2015

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  80. Geometrical and band-structure effects on phonon-limited hole mobility in rectangular cross-sectional germanium nanowires

    Tanaka H., Mori S., Morioka N., Suda J., Kimoto T.

    JOURNAL OF APPLIED PHYSICS   Vol. 116 ( 23 )   2014.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    We calculated the phonon-limited hole mobility in rectangular cross-sectional [001], [110], [111], and [112]-oriented germanium nanowires, and the hole transport characteristics were investigated. A tight-binding approximation was used for holes, and phonons were described by a valence force field model. Then, scattering probability of holes by phonons was calculated taking account of hole-phonon interaction atomistically, and the linearized Boltzmann's transport equation was solved to calculate the hole mobility at low longitudinal field. The dependence of the hole mobility on nanowire geometry was analyzed in terms of the valence band structure of germanium nanowires, and it was found that the dependence was qualitatively reproduced by considering an average effective mass and the density of states of holes. The calculation revealed that [110] germanium nanowires with large height along the [001] direction show high hole mobility. Germanium nanowires with this geometry are also expected to exhibit high electron mobility in our previous work, and thus they are promising for complementary metal-oxide-semiconductor (CMOS) applications.

    DOI: 10.1063/1.4904844

    Web of Science

    Scopus

  81. Impact of conduction type and doping density on thermal oxidation rate of SiC(0001)

    Kobayashi Takuma, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 7 ( 12 )   2014.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We discovered that the oxidation rate of SiC depends on the conduction type. The oxidation was faster in n-type SiC than in p-type SiC. The linear rate constant B/A was higher for n-type SiC than for p-type SiC, which may be caused by the stability of Si vacancies. The parabolic rate constant B was nearly constant for n-type SiC, whereas it decreased dramatically for heavily doped p-type SiC. Secondary-ion mass spectrometry measurements revealed that a high density of Al atoms was incorporated in the oxide of p-type SiC, which may hinder the diffusion of O2 or COx.

    DOI: 10.7567/APEX.7.121301

    Web of Science

    Scopus

  82. Decay curve analyses in carrier lifetime measurements of p- and n-type 4H-SiC epilayers

    Hayashi Toshihiko, Okuda Takafumi, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 11 )   2014.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The impacts of the ambipolar diffusion constant and surface recombination in carrier lifetime measurements of p- and n-type 4H-SiC epilayers are investigated in detail by comparing a numerical simulation based on a diffusion equation and the measurement of microwave photoconductance decay (μ-PCD) curves measured from 4H-SiC epilayers. The simulation reveals that the shapes of decay curves of excess carrier concentration in epilayers, which defines the effective carrier lifetime, are different between p- and n-type 4H-SiC under a low-level injection condition, even when the bulk lifetime and the surface recombination velocity are fixed to the same values for p- and n-type epilayers. In experiments, the shapes of the microwave photoconductance decay curves measured from p- and n-type 4H-SiC epilayers show a similar tendency to the simulation results under a low-level injection condition. This is attributed to the difference in the dependence of the ambipolar diffusion constant on the excess carrier concentration for p- and n-type 4H-SiC. The comparison of μ-PCD decay curves obtained from 50-μm-thick epilayers with different surface passivation indicates that the surface recombination velocity on the epilayer passivated with deposited SiO2 followed by NO annealing is about one order of magnitude lower than that of the epilayer passivated with the dry oxide.

    DOI: 10.7567/JJAP.53.111301

    Web of Science

    Scopus

  83. Temperature dependence of optical absorption coefficient of 4H-and 6H-SiC from room temperature to 300 degrees C

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 10 )   2014.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Optical absorption coefficients of 4H- and 6H-SiC were measured at cutoff wavelengths from a value of 0 to 400-500cm-1 at various temperatures that is from room temperature to 300 °C. The redshift of the absorption edge with increasing temperature was observed. It is caused by a decrease in bandgap energy and a change in phonon occupation with increasing temperature. By considering TA-, LA-, and TO-mode phonon-assisted indirect transitions, the measured data are well fitted using a theoretical model. The obtained parameters are reported.

    DOI: 10.7567/JJAP.53.108003

    Web of Science

    Scopus

  84. Formation mechanism of threading-dislocation array in AlN layers grown on 6H-SiC (0001) substrates with 3-bilayer-high surface steps

    Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 105 ( 7 )   2014.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    We grew AlN layers on 6H-SiC (0001) substrates with three Si-C bilayer high (0.75nm) steps. In the AlN layers, most of the threading dislocations (TDs) were arranged in rows. The TD row consisted of arrays of a half-loop dislocation, which was formed by an AlN/SiC interfacial dislocation along the step edges of the SiC substrate surfaces and a TD pair at both ends. The configuration of the interfacial dislocation was highly relevant with two-dimensional AlN nuclei at the initial stage of growth. We concluded that the half-loop dislocation arrays were generated in the AlN nucleus coalescence over the SiC step edges. © 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4892807

    Web of Science

    Scopus

  85. Enhancement of carrier lifetime in lightly Al-doped p-type 4H-SiC epitaxial layers by combination of thermal oxidation and hydrogen annealing

    Okuda T., Miyazawa T., Tsuchida H., Kimoto T., Suda J.

    Applied Physics Express   Vol. 7 ( 8 )   2014.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We investigated the enhancement of carrier lifetime in lightly Al-doped p-type 4H-SiC epilayers (NA ≃ 2 × 1014cm-3) by postgrowth processing. A carrier lifetime of 2.8 ìs in an as-grown epilayer is increased to 5.1 μs by carbon vacancy elimination, i.e., thermal oxidation at 1400 °C for 48 h. It reaches 10 μs by subsequent hydrogen annealing at 1000 °C for 10 min. The carrier lifetime in the as-grown epilayer is also increased to 4.0 μs by only hydrogen annealing. These results suggest that, in addition to carbon vacancy, there is another lifetime killer in p-type SiC, which cannot be eliminated by thermal oxidation but can be passivated by hydrogen annealing. © 2014 The Japan Society of Applied Physics.

    DOI: 10.7567/APEX.7.085501

    Scopus

  86. Conduction-type dependence of thermal oxidation rate on SiC(0001)

    Kobayashi T., Suda J., Kimoto T.

    IMFEDK 2014 - 2014 International Meeting for Future of Electron Devices, Kansai     2014.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IMFEDK 2014 - 2014 International Meeting for Future of Electron Devices, Kansai  

    The conduction-type dependent thermal oxidation rate in SiC was discovered. The oxidation was performed for SiC(0001) with nitrogen doping (n-type) in the range from 2.0×1016cm-3to 1.0×1019cm-3, and aluminum doping (p-type) in the range from 2.0×1015cm-3to 1.0×1019cm-3, exhibiting a clear dependence. For n-type SiC the oxide thickness increases for higher doping density, and for p-type the thickness decreases. Note that in the case of Si oxidation, there exists very little difference of oxidation rate between the conduction types in such low doping density, and the dependence is peculiar to SiC. The authors speculate the difference originates from the difference in carrier (electron/hole) density during the oxidation, which can reasonably explain the difference in the oxidation rate between Si and SiC.

    DOI: 10.1109/IMFEDK.2014.6867060

    Scopus

  87. Phonon-Limited Electron Mobility in Rectangular Cross-Sectional Ge Nanowires

    Tanaka Hajime, Mori Seigo, Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 61 ( 6 ) page: 1993 - 1998   2014.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    The phonon-limited electron mobility in rectangular cross-sectional germanium (Ge) nanowires (NWs) with various orientations was theoretically investigated. The electronic states were calculated by a tight-binding model and the phononic states were calculated by a valence force field model. Then, transition probability was calculated by Fermi's golden rule, and Boltzmann's transport equation was solved for calculating lowfield mobility. The electron mobility of Ge NWs strongly depends on the wire orientations and cross-sectional shapes, and this dependence can be explained by the conduction band structure of Ge NWs. Among several geometries investigated in this paper, [110]-oriented NWs with wider width along [001] showed the highest electron mobility at low carrier concentration, and [112] NWs with wider width along [110] showed the highest electron mobility at high carrier concentration. This result indicates that these kinds of Ge NWs are suitable as n-channel material. © 1963-2012 IEEE.

    DOI: 10.1109/TED.2014.2318896

    Web of Science

    Scopus

  88. Quantitative comparison between Z<inf>1/2</inf> center and carbon vacancy in 4H-SiC

    Kawahara K., Thang Trinh X., Tien Son N., Janzén E., Suda J., Kimoto T.

    Journal of Applied Physics   Vol. 115 ( 14 )   2014.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    In this study, to reveal the origin of the Z1/2 center, a lifetime killer in n-type 4H-SiC, the concentrations of the Z1/2 center and point defects are compared in the same samples, using deep level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR). The Z1/2 concentration in the samples is varied by irradiation with 250 keV electrons with various fluences. The concentration of a single carbon vacancy (VC) measured by EPR under light illumination can well be explained with the Z1/2 concentration derived from C-V and DLTS irrespective of the doping concentration and the electron fluence, indicating that the Z1/2 center originates from a single VC. © 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4871076

    Scopus

  89. 4H-SiC MISFETs With 4H-AlN Gate Insulator Isopolytypically Grown on 4H-SiC (11(2)over-bar0)

    Horita Masahiro, Noborio Masato, Kimoto Tsunenobu, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 35 ( 3 ) page: 339 - 341   2014.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    4H silicon carbide (4H-SiC) metal-insulator-semiconductor field-effect transistors (MISFETs) with 4H aluminum nitride (4H-AlN) gate insulators have been demonstrated. The 4H-AlN layers are isopolytypically grown on 4H-SiC (1120) by molecular-beam epitaxy. Gate controlled transistor operation was realized using the AlN/SiC MISFETs. The MISFETs exhibit a low gate leakage current (<10-10~A) and normally on characteristics with a threshold voltage of approximately-10~V and a field-effect mobility of 0.5 cm 2V-1s-1. Capacitance-voltage measurements of AlN/SiC MIS capacitors reveal a large negative flat band shift of-10.9~V, which is consistent with the normally on characteristics. © 2014 IEEE.

    DOI: 10.1109/LED.2014.2299557

    Web of Science

    Scopus

  90. Effect of ultrathin AIN spacer on electronic properties of GaN/SiC heterojunction bipolar transistors

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 3 )   2014.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    GaN/SiC heterojunction bipolar transistors (HBTs) with an ultrathin AlN spacer layer at the n-GaN/p-SiC emitter junction are proposed for the control of the electronic properties of GaN/SiC heterojunctions. The insertion of an AlN spacer is found to be promising in terms of improving electron injection efficiency owing to the reduced potential barrier (0.54 eV) to electron injection and reduced recombination via interface traps. We also investigated the effect of pre-irradiation of active nitrogen atoms (N*) prior to AlN growth for the control of the electronic properties of GaN/ AlN/SiC heterojunctions. We found that the potential barrier was further reduced to 0.46 eV by N* pre-irradiation. The HBT structure was successfully fabricated using our newly developed process featuring ion implantation and Pd ohmic contacts to obtain a low contact resistivity to a p-SiC base at a temperature as low as 600 °C. A fabricated HBT without an AlN layer showed a low current gain (α ∼ 0.001), whereas the GaN/ AlN/SiC HBT showed improved current gains of 0.1 in the case of using a 1-nm-thick AlN spacer without N* pre-irradiation and 0.2 in the case of using a 2-nm-thick AlN spacer with N* pre-irradiation. © 2014 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.53.034101

    Web of Science

    Scopus

  91. Quantum-confinement effects on conduction band structure of rectangular cross-sectional GaAs nanowires

    Tanaka H., Morioka N., Mori S., Suda J., Kimoto T.

    JOURNAL OF APPLIED PHYSICS   Vol. 115 ( 5 )   2014.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The conduction band structure and electron effective mass of GaAs nanowires with various cross-sectional shapes and orientations were calculated by two methods, a tight-binding method and an effective mass equation taking the bulk full-band structure into account. The effective mass of nanowires increases as the cross-sectional size decreases, and this increase in effective mass depends on the orientations and substrate faces of nanowires. Among [001], [110], and [111]-oriented rectangular cross-sectional GaAs nanowires, [110]-oriented nanowires with wider width along the [001] direction showed the lightest effective mass. This dependence originates from the anisotropy of the Γ valley of bulk GaAs. The relationship between effective mass and bulk band structure is discussed. © 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4864490

    Web of Science

    Scopus

  92. Identification of dislocations in 4H-SiC epitaxial layers and substrates using photoluminescence imaging

    Kawahara Chihiro, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 2 )   2014.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Dislocations in n- and p-type substrates as well as in epitaxial layers (epilayers) were clearly identified using a photoluminescence (PL) imaging technique. Dislocations in epilayers show large/small bright spots or lines in infrared PL images, which correspond to threading screw/edge dislocations (TSDs/TEDs) or basal plane dislocations (BPDs), respectively. In contrast, dislocations in substrates exhibit large/small dark spots or dark lines in infrared PL images, corresponding to TSDs/TEDs or BPDs, respectively. These different features (bright/dark contrast) of dislocations may originate from the different densities of point defects or impurities. © 2014 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.53.020304

    Web of Science

    Scopus

  93. Etching-limiting process and origin of loading effects in silicon etching with hydrogen chloride gas

    Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 53 ( 1 )   2014.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The etching-limiting step in slow Si etching with HCl/H2 at atmospheric pressure was investigated. The etching was performed at a low etching rate below 10nm/min in the temperature range of 1000-1100 °C. In the case of bare Si etching, it was confirmed that the etching rate showed little temperature dependence and was proportional to the equilibrium pressure of the etching by-product SiCl2 calculated by thermochemical analysis. In addition, the etching rates of Si(100) and (110) faces were almost the same. These results indicate that SiCl2 diffusion in the gas phase is the rate-limiting step. In the etching of the Si surface with SiO2 mask patterns, a strong loading effect (mask/opening pattern dependence of the etching rate) was observed. The simulation of the diffusion of gas species immediately above the Si surface revealed that the loading effect was attributed to the pattern-dependent diffusion of SiCl2.© 2014 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.53.016502

    Web of Science

    Scopus

  94. Conduction-Type Dependence of Thermal Oxidation Rate on SiC(0001)

    Kobayashi Takuma, Suda Jun, Kimoto Tsunenobu

    2014 IEEE INTERNATIONAL MEETING FOR FUTURE OF ELECTRON DEVICES, KANSAI (IMFEDK)     2014

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  95. Fabrication of electrostatically actuated 4H-SiC microcantilever resonators by using n/p/n epitaxial structures and doping-selective electrochemical etching

    Sato K., Adachi K., Okamoto H., Yamaguchi H., Kimoto T., Suda J.

    Materials Science Forum   Vol. 778-780   page: 780 - 783   2014

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    We fabricated electrostatically actuated single-crystalline 4H-SiC microcantilever resonators. To realize a narrow gap between cantilevers and substrate, we etched a thin p-type SiC layer in n/p/n multilayer structure by doping-selective electrochemical etching. The resonant characteristics of the fabricated 4H-SiC microcantilevers were investigated under a vacuum condition. Electrostatic actuation of microcantilevers was successfully performed by applying 10 mVrms ac voltage with 20 mV dc bias. The quality factor of 4H-SiC microcantilevers was above 100,000, which is about ten times higher than the quality factor of Si cantilevers with the same structure. Resonant characteristics were almost identical for mechanical actuation and electrostatic actuation. © (2014) Trans Tech Publications, Switzerland.

    DOI: 10.4028/www.scientific.net/MSF.778-780.780

    Scopus

  96. Identification of the negative carbon vacancy at quasi-cubic site in 4H-SIC by EPR and theoretical calculations

    Trinh X.T., Szász K., Hornos T., Kawahara K., Suda J., Kimoto T., Gali A., Janzén E., Son N.T.

    Materials Science Forum   Vol. 778-780   page: 285 - 288   2014

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, V-C(h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, V-C (k). The identification is further supported by hyperfine calculations. © (2014) Trans Tech Publications, Switzerland.

    DOI: 10.4028/www.scientific.net/MSF.778-780.285

    Scopus

  97. Ion Implantation Technology in SiC for Power Device Applications

    Kimoto Tsunenobu, Kawahara Koutaro, Niwa Hiroki, Kaji Naoki, Suda Jun

    2014 INTERNATIONAL WORKSHOP ON JUNCTION TECHNOLOGY (IWJT)     page: 1 - 6   2014

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  98. Orientation and Size Effects on Phonon-limited Hole Mobility in Rectangular Cross-sectional Germanium Nanowires

    Tanaka Hajime, Mori Seigo, Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    2014 IEEE SILICON NANOELECTRONICS WORKSHOP (SNW)     2014

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  99. Ion implantation technology in SiC for power device applications

    Kimoto T., Kawahara K., Niwa H., Kaji N., Suda J.

    2014 International Workshop on Junction Technology, IWJT 2014     page: 1 - 6   2014

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2014 International Workshop on Junction Technology, IWJT 2014  

    Silicon carbide (SiC) is a newly-emerging wide bandgap semiconductor, by which high-voltage, low-loss power devices can be realized owing to its superior properties. Because of its strong bonding energy and thermal stability, however, special cares must be paid to form high-quality junctions by ion implantation. This paper reviews present status and remaining issues of ion implantation technology in SiC. Requirements of hot implantation and high-temperature annealing are discussed in terms of electrical activation, defect generation, and junction characteristics. Furthermore, recent progress in junction termination for high-voltage SiC devices by using ion implantation is described. © 2014 IEEE.

    DOI: 10.1109/IWJT.2014.6842018

    Scopus

  100. 100 mm diameter mono-crystalline 4H-SiC/polycrystalline-SiC bonded wafers fabricated by SAB for power device

    Yagi K., Hatta N., Sakata T., Minami A., Kawahara T., Uchida H., Imaoka K., Okuda T., Suda J., Kurashima Y., Takagi H.

    Proceedings of 2014 4th IEEE International Workshop on Low Temperature Bonding for 3D Integration, LTB-3D 2014     2014

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of 2014 4th IEEE International Workshop on Low Temperature Bonding for 3D Integration, LTB-3D 2014  

    We have developed 100mm in diameter 4H-SiC/poly-SiC bonded wafer by SAB method. The SiC bonded wafer demonstrated an excellent thermal stability against device processing temperature. SBDs fabricated on the SiC bonded wafer exhibited good I-V characteristics. These results suggest that it is a promising alternative wafer for SiC power device. © 2014 IEEE.

    DOI: 10.1109/LTB-3D.2014.6886195

    Scopus

  101. Negative- U carbon vacancy in 4 H -SiC: Assessment of charge correction schemes and identification of the negative carbon vacancy at the quasicubic site

    Trinh X.T., Szász K., Hornos T., Kawahara K., Suda J., Kimoto T., Gali A., Janzén E., Son N.T.

    Physical Review B - Condensed Matter and Materials Physics   Vol. 88 ( 23 )   2013.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physical Review B - Condensed Matter and Materials Physics  

    The carbon vacancy (VC) has been suggested by different studies to be involved in the Z1/Z2 defect-a carrier lifetime killer in SiC. However, the correlation between the Z1/Z2 deep level with VC is not possible since only the negative carbon vacancy (VC-) at the hexagonal site, VC-(h), with unclear negative-U behaviors was identified by electron paramagnetic resonance (EPR). Using freestanding n-type 4H-SiC epilayers irradiated with low energy (250 keV) electrons at room temperature to introduce mainly VC and defects in the C sublattice, we observed the strong EPR signals of VC-(h) and another S = 1/2 center. Electron paramagnetic resonance experiments show a negative-U behavior of the two centers and their similar symmetry lowering from C3v to C1h at low temperatures. Comparing the 29Si and 13C ligand hyperfine constants observed by EPR and first principles calculations, the new center is identified as VC-(k). The negative-U behavior is further confirmed by large scale density functional theory supercell calculations using different charge correction schemes. The results support the identification of the lifetime limiting Z1/Z2 defect to be related to acceptor states of the carbon vacancy. © 2013 American Physical Society.

    DOI: 10.1103/PhysRevB.88.235209

    Scopus

  102. Growth, Electrical Characterization, and Electroluminescence of GaN/SiC Heterojunction Diodes and Bipolar Transistors Fabricated on SiC Off-Axis Substrates

    Miyake Hiroki, Amari Koichi, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 52 ( 12 )   2013.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The growth, electrical characterization, and electroluminescence (EL) of GaN/SiC heterojunction bipolar transistors (HBTs) are presented. GaN grown on off-axis SiC by molecular beam epitaxy showed step bunching owing to the large off-angle of SiC substrates, which contributed to the annihilation of edge dislocations. We investigated the impact of base doping concentration and SiC polytype (4H and 6H) on the characteristics of GaN/SiC heterojunction diodes. By utilizing a reduced doping concentration of 1 × 1018 cm -3 instead of 1 × 1019 cm-3, we suppressed the tunneling current via interface traps, resulting in an improved rectifying behavior in the diodes. Capacitance-voltage (C-V) and EL characteristics revealed that the band lineup of GaN/SiC is of type II, and 6H-SiC is better for electron injection. In accordance with diode characteristics, the fabricated GaN/SiC HBTs showed an improved common-base current gain of 0.03 by employing a reduced base doping concentration of 1 × 1018 cm-3 and 6H-SiC, whereas a current gain below 1 × 10-4 was obtained in the HBTs with a base doping concentration of 1 × 1019 cm-3. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.52.124102

    Web of Science

    Scopus

  103. Improvement of Carrier Lifetimes in Highly Al-Doped p-Type 4H-SiC Epitaxial Layers by Hydrogen Passivation

    Okuda Takafumi, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 6 ( 12 )   2013.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    Carrier lifetimes in a highly Al-doped p-type epilayer (NA = 1 × 1018 cm-3) are investigated by differential microwave photoconductance decay (μ-PCD) measurements. A carrier lifetime of 310 ns in the as-grown p-type epilayer decreases to 90 ns by thermal treatment in Ar, O2, or N2 atmospheres (>700 °C), and recovers to 300 ns by H2 annealing (>750 °C). Hydrogen is detected at a concentration of (2-3) × 1015 cm-3 in the H2-annealed epilayer. These results suggest that a lifetime killer exists in the p-type epilayer, limiting the carrier lifetime to 90 ns and is passivated by hydrogen annealing, resulting in the improved carrier lifetime of 300 ns. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/APEX.6.121301

    Web of Science

    Scopus

  104. Size and geometric effects on conduction band structure of GaAs nanowires

    Tanaka H., Morioka N., Mori S., Suda J., Kimoto T.

    IMFEDK 2013 - 2013 International Meeting for Future of Electron Devices, Kansai     page: 118 - 119   2013.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IMFEDK 2013 - 2013 International Meeting for Future of Electron Devices, Kansai  

    The conduction band structure of GaAs nanowires with various cross-sectional shapes and orientations was calculated by a tight-binding model and an effective mass equation taking the bulk full-band structure into account. The effective mass of nanowires increases as the cross-sectional size decreases. However, the amount of the increase in mass is strongly dependent on the wire orientations and substrate faces of nanowires, which originates from the anisotropy of Γ valley of bulk GaAs. © 2013 IEEE.

    DOI: 10.1109/IMFEDK.2013.6602267

    Scopus

  105. AlGaN/SiC Heterojunction Bipolar Transistors Featuring AlN/GaN Short-Period Superlattice Emitter

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 60 ( 9 ) page: 2768 - 2775   2013.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Growth and electrical characterization of aluminum gallium nitride (AlGaN)/SiC heterojunction bipolar transistors (HBTs) featuring AlN/GaN short-period superlattice as a quasi-AlGaN emitter are presented. The AlN/GaN superlattice emitter was grown by molecular beam epitaxy on off-axis SiC, which showed adequate structural and electronic properties as the emitter of the HBTs. We investigated the impact of Al composition in the emitter on the transport characteristics and current gain of the HBTs. Using Al composition of over 0.5, we achieved type-I band alignment in AlGaN/SiC, and suppressed the tunneling current via interface traps, resulting in an improved current gain of up to 2.7. Toward further improvement of current gain, we also investigated the effect of n-SiC spacer between n-AlGaN and p-SiC and p-SiC base width. Using 200-nm-thick n-SiC spacer and 250-nm-thick p-SiC base layer, we achieved an improved current gain of 13 owing to the reduced interface and bulk recombination. © 1963-2012 IEEE.

    DOI: 10.1109/TED.2013.2273499

    Web of Science

    Scopus

  106. Coherent Growth of AlN/GaN Short-Period Superlattice with Average GaN Mole Fraction of up to 20% on 6H-SiC(0001) Substrates by Plasma-Assisted Molecular-Beam Epitaxy

    Kaneko Mitsuaki, Kikuchi Ryosuke, Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 52 ( 8 )   2013.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    To obtain a high-crystalline-quality AlN/GaN short-period superlattice with higher average GaN mole fraction, the effects of the thicknesses of AlN barrier and GaN well layers on the superlattice growth were investigated. Coherent growth with an average GaN mole fraction of 20% was realized by reducing the AlN barrier layer thickness to 8 bilayers (BL) while keeping the GaN well layer thickness at 2 BL. Further reduction in the AlN barrier layer thickness resulted in lattice relaxation and degradation of the crystalline quality. Grown layers with various well and barrier thicknesses were investigated by transmission electron microscopy, X-ray diffraction, and atomic force microscopy. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.52.08JE21

    Web of Science

    Scopus

  107. Ultrahigh-Voltage SiC PiN Diodes with an Improved Junction Termination Extension Structure and Enhanced Carrier Lifetime

    Kaji Naoki, Niwa Hiroki, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 52 ( 7 )   2013.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Ultrahigh-voltage SiC PiN diodes with an improved junction termination extension (JTE) structure and improved forward characteristics are presented in this paper. An improved space-modulated JTE (SM-JTE) structure was designed by device simulation, and a breakdown voltage of over 17 kV was obtained in a wider range of JTE dose with the improved SM-JTE. In addition, a lifetime enhancement process (thermal oxidation) was performed to improve the forward characteristics. The on-resistance of the SiC PiN diodes with the lifetime enhancement process was reduced to 13m°Cm2 at 150°C compared with that of the SiC PiN diodes with the conventional process (32m°Cm2). © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.52.070204

    Web of Science

    Scopus

  108. Optical Properties of Highly Strained AlN Coherently Grown on 6H-SiC(0001)

    Kaneko Mitsuaki, Okumura Hironori, Ishii Ryota, Funato Mitsuru, Kawakami Yoichi, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 6 ( 6 )   2013.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The optical properties of wurtzite AlN under large compressive strain are investigated by photoluminescence and optical reflectivity measurements with two different geometries. The AlN layer was coherently grown on 6H-SiC(0001), resulting in strains of ∈xx = ∈yy = -9.6 × 10-3 and ∈zz = 5.12 × 10-3, as confirmed by high-resolution X-ray diffraction. Free exciton transitions were clearly observed. The transition energy of A free exciton (with Γ1 symmetry) was estimated to be 6.246 eV at 10 K. The large energy shift of the free exciton transition with respect to the transition in unstrained AlN was well explained by the reported deformation potentials of AlN. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/APEX.6.062604

    Web of Science

    Scopus

  109. Single-crystalline 4H-SiC micro cantilevers with a high quality factor

    Adachi K., Watanabe N., Okamoto H., Yamaguchi H., Kimoto T., Suda J.

    Sensors and Actuators, A: Physical   Vol. 197   page: 122 - 125   2013.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Sensors and Actuators, A: Physical  

    Single-crystalline 4H-SiC micro cantilevers were fabricated by doping-type selective electrochemical etching of 4H-SiC. Using this method, n-type 4H-SiC cantilevers were fabricated on a p-type 4H-SiC substrate, and resonance characteristics of the fabricated 4H-SiC cantilevers were investigated under a vacuum condition. The resonant frequencies agreed very well with the results of numerical simulations. The maximum quality factor in first-mode resonance of the 4H-SiC cantilevers was 230,000. This is 10 times higher than the quality factor of conventional 3C-SiC cantilevers fabricated on an Si substrate. © 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.sna.2013.04.014

    Scopus

  110. Deep Levels Generated by Thermal Oxidation in n-Type 4H-SiC

    Kawahara Koutarou, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 6 ( 5 )   2013.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The Z1/2 center (EC - 0:67 eV), which is a lifetime killer in n-type 4H-SiC epilayers, is reduced by thermal oxidation. The oxidation, however, simultaneously generates other deep levels: ON1 (E C - 0:84 eV) and ON2 (EC - 1:1 eV) centers. From the behaviors (generation condition, thermal stability, and change in the depth profiles) of the ON1 and ON2 centers in samples (i) oxidized in O2, (ii) implanted with C+ or Si+ atoms, and (iii) oxidized in N2O (or NO), we suggest that these defects may originate from the same defect in different charge states, related to both carbon interstitials and N atoms. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/APEX.6.051301

    Web of Science

    Scopus

  111. Investigation on origin of Z<inf>1/2</inf> center in SiC by deep level transient spectroscopy and electron paramagnetic resonance

    Kawahara K., Trinh X.T., Son N.T., Janzén E., Suda J., Kimoto T.

    Applied Physics Letters   Vol. 102 ( 11 )   2013.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    The Z1/2 center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient spectroscopy (DLTS), we show that the Z1/2 center is responsible for the carrier compensation in n-type 4H-SiC epilayers irradiated by low-energy (250 keV) electrons. The concentration of the Z1/2 defect obtained by C-V and DLTS correlates well with that of the carbon vacancy (VC) determined by electron paramagnetic resonance, suggesting that the Z1/2 deep level originates from VC. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4796141

    Scopus

  112. Effects of Nitridation on 4H-SiC MOSFETs Fabricated on Various Crystal Faces

    Nanen Yuichiro, Kato Muneharu, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 60 ( 3 ) page: 1260 - 1262   2013.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    Effects of nitric oxide (NO) and nitrous oxide (N2O) annealing on 4H-SiCmetal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on the (0001), (000-1), and (11-20) faces are investigated. MOSFETs on (11-20) exhibited high channel mobility (108 cm2/V s) compared to those on (0001) (29-37 cm2/V s) and (000-1) (39-46 cm2/V s). The MOSFET characteristics are discussed in terms of oxidation taking place during the nitridation annealing and crystal faces.

    DOI: 10.1109/TED.2012.2236333

    Web of Science

    Scopus

  113. Orientation and Shape Effects on Ballistic Transport Properties in Gate-All-Around Rectangular Germanium Nanowire nFETs

    Mori Seigo, Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 60 ( 3 ) page: 944 - 950   2013.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    The electron transport properties of square and rectangular cross-sectional germanium nanowire (GeNW) field-effect transistors (FETs) with [001], [110], [111], and [112] crystal orientations are investigated. The electronic states of GeNWs are calculated by using an sp^{3}d^{5}s\ast tight-binding model coupled to a Poisson equation self-consistently. A semiclassical ballistic FET model is used to evaluate the electron transport characteristics. For the square cross section, electron injection velocity dominates the drive current in GeNW FETs because the inversion electron density in the GeNW channels is mainly determined by the capacitance of the gate insulator, and a [110] GeNW FET achieves the highest drive current of all the orientations. In the case of rectangular cross section, the electron density in GeNWs is dependent on their orientations and cross-sectional geometries due to the small quantum capacitance, and the difference of the density of states of GeNWs significantly affects the drive current. A [112] GeNW FET on a (\hbox{1}\bar{\hbox{1}}\hbox{0} ) face exhibits the highest injection velocity of all the calculated FETs but low drive current because of its insufficient density of states. As a result, a [110] GeNW FET on a (001) face, which has both large density of states and high injection velocity, achieves the highest drive current. © 1963-2012 IEEE.

    DOI: 10.1109/TED.2013.2237779

    Web of Science

    Scopus

  114. Deep levels generated by thermal oxidation in p-type 4H-SiC

    Kawahara Koutarou, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 113 ( 3 )   2013.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Thermal oxidation is an effective method to reduce deep levels, especially the Z1/2-center (EC - 0.67 eV), which strongly suppresses carrier lifetimes in n-type 4H-SiC epilayers. The oxidation, however, simultaneously generates other deep levels, HK0 (EV + 0.79 eV) and HK2 (EV + 0.98 eV) centers, within the lower half of the bandgap of SiC, where the HK0 center is a dominant deep level with a concentration of about 1 × 1013 cm-3 after oxidation. By comparing deep levels observed in three sets of p-type 4H-SiC: oxidized, electron-irradiated, and C+- or Si+-implanted samples, we find that the HK0 and HK2 centers are complexes including carbon interstitials such as the di-carbon interstitial or di-carbon antisite. Other defects observed in p-type 4H-SiC after electron irradiation or after C+/Si+ implantation are also studied. © 2013 American Institute of Physics.

    DOI: 10.1063/1.4776240

    Web of Science

    Scopus

  115. Long Photoconductivity Decay Characteristics in p-Type 4H-SiC Bulk Crystals

    Okuda Takafumi, Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 52 ( 1 )   2013.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    We investigated the photoconductivity decay characteristics of p-type 4H-SiC bulk crystals by differential microwave photoconductance decay (μ-PCD) measurements using a 349-nm laser as an excitation source. The decay time at room temperature was 2600 μs, which is much longer than that of n-type 4H-SiC bulk crystals (40 ns). Decay time decreased with increasing temperature, resulting in 120 μs at 250 °C, and the activation energy of decay time was determined to be 140 ± 10 meV. Long decay characteristics were also observed by below-band-gap excitation at 523 nm. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/JJAP.52.010202

    Web of Science

    Scopus

  116. Junction technology in SiC for high-voltage power devices

    Kimoto T., Kawahara K., Niwa H., Okuda T., Suda J.

    Extended Abstracts of the 13th International Workshop on Junction Technology 2013, IWJT 2013     page: 54 - 57   2013

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Extended Abstracts of the 13th International Workshop on Junction Technology 2013, IWJT 2013  

    In electric power conversion systems of power infrastructures, electric vehicles, and power supplies, Si-based power semiconductor devices are employed as a key hardware. Reduction of power dissipation in the conversion systems is strongly required for energy saving. In particular, ultrahigh-voltage power converters with high efficiency are essential to realize a stable and highly efficient electric power network by optimizing the use of solar power and wind-generated power in the future. The efficiency of power converters/inverters strongly relies on the performance of power semiconductor devices employed in the power electronic systems. Silicon carbide (SiC) is a newly-emerging wide bandgap semiconductor, by which high-voltage, low-loss power devices can be realized owing to its superior properties [1-3]. The major features of SiC power devices include high-voltage blocking capability, low on-state resistance, fast switching speed, and high-temperature operation. © 2013 IEEE.

    DOI: 10.1109/IWJT.2013.6644492

    Scopus

  117. Size and Geometric Effects on Conduction Band Structure of GaAs Nanowires

    Tanaka Hajime, Morioka Naoya, Mori Seigo, Suda Jun, Kimoto Tsunenobu

    2013 IEEE INTERNATIONAL MEETING FOR FUTURE OF ELECTRON DEVICES, KANSAI (IMFEDK2013)     2013

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  118. 21-kV SiC BJTs With Space-Modulated Junction Termination Extension

    Miyake Hiroki, Okuda Takafumi, Niwa Hiroki, Kimoto Tsunenobu, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 33 ( 11 ) page: 1598 - 1600   2012.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    We report here 20-kV-class small-area (0.035 mm 2 ) 4H-SiC bipolar junction transistors. We implemented edge termination techniques featuring two-zone junction termination extension and space-modulated rings. on-state characteristics showed a current gain of 63 and a specific on-resistance of 321 mΩ cm 2, which is slightly below the SiC unipolar limit. We achieved the open-base blocking voltage of 21 kV at a leakage current of 0.1 mA/cm 2 , which is the highest blocking voltage among any semiconductor switching devices. © 2012 IEEE.

    DOI: 10.1109/LED.2012.2215004

    Web of Science

    Scopus

  119. Thermo-Optic Coefficients of 4H-SiC, GaN, and AIN for Ultraviolet to Infrared Regions up to 500 degrees C

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 51 ( 11 )   2012.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The temperature dependence of the refractive indices of 4H-SiC, GaN, and AlN were determined in a wavelength range from the near band edge (392 nm for 4H-SiC, 367nm for GaN, and 217nm for AlN) to infrared (1700 nm) and a temperature range from room temperature to 500 °C. Optical interference measurements with vertical incidence along a c-axis configuration were employed to precisely evaluate ordinary refractive indices. Near the band-edge region, the temperature dependence of the refractive index mainly originates from the temperature change of the bandgap. At 450 nm, the thermo-optic coefficients of 4H-SiC, GaN, and AlN were measured to be 7:8 × 10 -5, 1:6 × 10 -4, and 3:6 × 10 -5 K -1, respectively. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.51.112101

    Web of Science

    Scopus

  120. Negative-U system of carbon vacancy in 4H-SiC

    Son N.T., Trinh X.T., Løvlie L.S., Svensson B.G., Kawahara K., Suda J., Kimoto T., Umeda T., Isoya J., Makino T., Ohshima T., Janzén E.

    Physical Review Letters   Vol. 109 ( 18 )   2012.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physical Review Letters  

    Using electron paramagnetic resonance (EPR), energy levels of the carbon vacancy (V C) in 4H-SiC and its negative-U properties have been determined. Combining EPR and deep-level transient spectroscopy we show that the two most common defects in as-grown 4H-SiC-the Z 1/2 lifetime-limiting defect and the EH 7 deep defect-are related to the double acceptor (2-|0) and single donor (0|+) levels of V C, respectively. © 2012 American Physical Society.

    DOI: 10.1103/PhysRevLett.109.187603

    Scopus

  121. Orientation and size effects on ballistic electron transport properties in gate-all-around rectangular germanium nanowire FETs

    Mori S., Morioka N., Suda J., Kimoto T.

    2012 IEEE Silicon Nanoelectronics Workshop, SNW 2012     2012.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2012 IEEE Silicon Nanoelectronics Workshop, SNW 2012  

    We calculated the conduction band structure of GeNWs by a tight-binding model and obtained the fundamental understanding of electron transport characteristics in [001], [110], [111], and [112] GeNW FETs. The simulation of ballistic electron transport revealed that [110] GeNW FETs on the (001) face achieve high drive current as well as high injection velocity, being the best choice for n-channel FETs. © 2012 IEEE.

    DOI: 10.1109/SNW.2012.6243360

    Scopus

  122. Breakdown Characteristics of 15-kV-Class 4H-SiC PiN Diodes With Various Junction Termination Structures

    Niwa Hiroki, Feng Gan, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 59 ( 10 ) page: 2748 - 2752   2012.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    15-kV-class 4H-SiC PiN diodes with various junction termination structures have been experimentally investigated. Employment of the space-modulated junction termination extension (SM-JTE) and the two-zone JTE have realized a breakdown voltage over 15 kV, corresponding to 93% of the parallel-plane breakdown voltage. The window of the implanted JTE dose to achieve the ultrahigh voltage has been enlarged, which indicates the robustness to the deviation of effective JTE dose. From the comparison of the experimental JTE-dose dependence of breakdown voltage with the numerical device simulation, a shift toward the heavier JTE-dose region was observed. To explain the phenomenon, effects of the charges at the SiO 2/SiC interface are discussed. © 2012 IEEE.

    DOI: 10.1109/TED.2012.2210044

    Web of Science

    Scopus

  123. Carrier Recombination in n-Type 4H-SiC Epilayers with Long Carrier Lifetimes

    Ichikawa Shuhei, Kawahara Koutarou, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 10 )   2012.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    A longest carrier lifetime of 33.2 μs was achieved by eliminating the Z 1/2 center via thermal oxidation at 1400 °C for 48 h and subsequent surface passivation with a nitrided oxide on a 220-μm-thick n-type 4H-SiC epilayer. By deep-level elimination, photoluminescence (PL) in the infrared region (wavelength: 700-950 nm) was remarkably enhanced at locations of threading dislocations. A threading screw dislocation exhibited much stronger infrared PL than a threading edge dislocation. The present results indicate that carrier recombination at extended defects becomes pronounced through the elimination of the Z 1/2 center in the epilayers. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.5.101301

    Web of Science

    Scopus

  124. Over-700-nm Critical Thickness of AlN Grown on 6H-SiC(0001) by Molecular Beam Epitaxy

    Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 10 )   2012.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We report on the critical thickness of AlN on SiC(0001). AlN was directly grown on 6H-SiC(0001) at 650 °C by rf-plasma-assisted molecular beam epitaxy. The growth layer had a relatively low threading dislocation density of 4 × 10 8-4 × 10 9 cm -2. Although the critical thickness of AlN on SiC(0001) is estimated to be 3.5nm using a Matthews-Blakeslee model, the critical thickness in our experiment was over 700 nm. Low dislocation density, a layer-by-layer growth mode, and low growth temperature may contribute to such a large critical thickness. Sharp and intense free exciton emission was observed in low-temperature PL measurements of the AlN layer. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.5.105502

    Web of Science

    Scopus

  125. Enhancement and control of carrier lifetimes in p-type 4H-SiC epilayers

    Hayashi T., Asano K., Suda J., Kimoto T.

    Journal of Applied Physics   Vol. 112 ( 6 )   2012.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Enhancement and control of carrier lifetimes in p-type 4H-SiC have been investigated. In this study, thermal oxidation and carbon ion implantation methods, both of which are effective for lifetime enhancement in n-type SiC, were attempted on 147-μm thick p-type 4H-SiC epilayers. Effects of surface passivation on carrier lifetimes were also investigated. The carrier lifetimes in p-type SiC could be enhanced from 0.9 μs (as-grown) to 2.6 μs by either thermal oxidation or carbon implantation and subsequent Ar annealing, although the improvement effect for the p-type epilayers was smaller than that for the n-type epilayers. After the lifetime enhancement, electron irradiation was performed to control the carrier lifetime. The distribution of carrier lifetimes in each irradiated region was rather uniform, along with successful lifetime control in the p-type epilayer in the range from 0.1 to 1.6 μs. © 2012 American Institute of Physics.

    DOI: 10.1063/1.4748315

    Scopus

  126. 4H-SiC pn Photodiodes with Temperature-Independent Photoresponse up to 300 degrees C

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 9 )   2012.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    4H-SiC pn photodiodes were fabricated and the temperature dependence of the photoresponse was measured for various wavelengths (280-365 nm) as a function of reverse-bias voltage. A temperature-independent photoresponse was obtained at 280nm illumination from room temperature to 300 °C under zero-bias condition. By applying reverse-bias voltage up to 150 V, the wavelength of the temperature-independent photoresponse was varied from 280 to 300 nm. The temperature-independent photoresponse was explained by the temperature dependence of optical absorption coefficient together with surface recombination effect. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.5.094101

    Web of Science

    Scopus

  127. Breakdown characteristics of 12-20 kV-class 4H-SiC PiN diodes with improved junction termination structures

    Niwa H., Feng G., Suda J., Kimoto T.

    Proceedings of the International Symposium on Power Semiconductor Devices and ICs     page: 381 - 384   2012.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the International Symposium on Power Semiconductor Devices and ICs  

    Ultrahigh-voltage 4H-SiC PiN diodes with improved junction termination extension (JTE) structures have been investigated. Breakdown characteristics of 4H-SiC PiN diodes with conventional single-zone JTE was shown to be severely affected by the charge near the SiO 2/SiC interface from experiment and device simulation. Taking the effect of the interface charge into account, and by using "Space-Modulated" JTE structure with a wide optimum JTE-dose window to tolerate the impact of interface charge, we achieved a breakdown voltage of 21.7 kV (81 % of the ideal breakdown voltage calculated from the epilayer structure), which is the highest breakdown voltage among any semiconductor devices ever reported. © 2012 IEEE.

    DOI: 10.1109/ISPSD.2012.6229101

    Scopus

  128. Fundamental study on junction termination structures for ultrahigh-voltage SiC PiN diodes

    Niwa H., Suda J., Kimoto T.

    IMFEDK 2012 - 2012 International Meeting for Future of Electron Devices, Kansai     page: 56 - 57   2012.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IMFEDK 2012 - 2012 International Meeting for Future of Electron Devices, Kansai  

    15 kV-class 4H-SiC PiN diodes with various junction termination extension (JTE) structures have been experimentally investigated. JTE-dose dependence of the breakdown voltage for conventional single and two-zone JTE showed a narrow window of optimum JTE-dose to obtain high breakdown voltage. To widen this window, space-modulated JTE (SM-JTE) was introduced. 4H-SiC PiN diodes with SM-JTE showed a highest breakdown voltage of 15 kV, and a widening of the optimum JTE-dose window to obtain ultrahigh-voltage was realized at the same time. © 2012 IEEE.

    DOI: 10.1109/IMFEDK.2012.6218579

    Scopus

  129. 21.7 kV 4H-SiC PiN Diode with a Space-Modulated Junction Termination Extension

    Niwa Hiroki, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 6 )   2012.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    Ultrahigh-voltage 4H-SiC mesa PiN diodes are fabricated and characterized. An original space-modulated two-zone junction termination extension (SM-two-zone JTE) has realized a laterally tapered profile of the JTE dose, which enlarged the tolerance to the deviation of effective JTE dose compared with a conventional two-zone JTE. We demonstrate a SiC PiN diode with a breakdown voltage of 21.7 kV (81% of the ideal breakdown voltage calculated from the epilayer structure), which is the highest breakdown voltage among any semiconductor devices ever reported. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.5.064001

    Web of Science

    Scopus

  130. Lattice mismatch and crystallographic tilt induced by high-dose ion-implantation into 4H-SiC

    Sasaki S., Suda J., Kimoto T.

    JOURNAL OF APPLIED PHYSICS   Vol. 111 ( 10 )   2012.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Lattice parameters of high-dose ion-implanted 4H-SiC were investigated with reciprocal space mapping (RSM). N, P, Al, or (CSi) ions were implanted into lightly doped epilayers to form a (330-520) nm-deep box profile with concentrations of 10 19-10 20 atoms/cm 3. After activation annealing at 1800 °C, RSM measurements were conducted. The RSM images for (0008) reflection revealed that high-dose ion implantation causes c-lattice expansion in implanted layers, irrespective of ion species. In addition, crystallographic tilt was observed after high-dose ion implantation. The tilt direction is the same for all the samples investigated; the c-axis of the implanted layers is inclined toward the ascending direction of the off-cut. The c-lattice mismatch and the tilt angle increased as the implantation dose increases, indicating that the implantation damage is responsible for the lattice parameter change. From these results and transmission electron microscopy observation, the authors conclude that the c-lattice mismatch and the crystallographic tilt are mainly caused by secondary defects formed after the ion-implantation and activation-annealing process. © 2012 American Institute of Physics.

    DOI: 10.1063/1.4720435

    Web of Science

    Scopus

  131. AlN/GaN Short-Period Superlattice Coherently Grown on 6H-SiC(0001) Substrates by Molecular Beam Epitaxy

    Kikuchi Ryosuke, Okumura Hironori, Kaneko Mitsuaki, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 5 ( 5 )   2012.5

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    We demonstrate the coherent growth of AIN/GaN short-period superlattice (SPSL) on 6H-SiC(0001) substrates by molecular beam epitaxy. A high-quality 5-nm-thick AIN layer was grown on SiC as a template layer, followed by the growth of AIN (12BL)/GaN (2BL) SPSL, which consists of 40 periods (total thickness: 140nm). The SPSL was coherently grown on SiC, and its threading dislocation density (TDD) was as low as 8 × 10 8cm -2. The SPSL, which had 3-BL-thick GaN layers, was relaxed, and the TDD increased to 8 × 10 10cm -2. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.5.051002

    Web of Science

    Scopus

  132. Current Transport Characteristics of Quasi-AlxGa1-xN/SiC Heterojunction Bipolar Transistors with Various Band Discontinuities

    Okuda Takafumi, Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 51 ( 4 )   2012.4

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The current transport characteristics of quasi-Al xGa 1-xN/SiC heterojunction bipolar transistors (HBTs) with various band discontinuities were investigated in a low-current range using a Gummel plot. In the low-current range, the base currents of the HBTs were dominated by recombination currents. The collector current characteristics of the HBTs in the low-current range were almost the same in spite of the various band discontinuities, and the ideality factor n was 1.0. The band discontinuities at the heterojunction had no effect on electron injection in the lowcurrent range. This is because the collector currents were dominated by diffusion process in the base region rather than by injection process at the AlGaN/SiC interface. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.51.04DP09

    Web of Science

    Scopus

  133. Analytical model for reduction of deep levels in SiC by thermal oxidation

    Kawahara Koutarou, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 111 ( 5 )   2012.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Two trap-reduction processes, thermal oxidation and C + implantation followed by Ar annealing, have been discovered, being effective ways for reducing the Z 12 center (E C - 0.67 eV), which is a lifetime killer in n-type 4H-SiC. In this study, it is shown that new deep levels are generated by the trap-reduction processes in parallel with the reduction of the Z 12 center. A comparison of defect behaviors (reduction, generation, and change of the depth profile) for the two trap-reduction processes shows that the reduction of deep levels by thermal oxidation can be explained by an interstitial diffusion model. Prediction of the defect distributions after oxidation was achieved by a numerical calculation based on a diffusion equation, in which interstitials generated at the SiO 2SiC interface diffuse to the SiC bulk and occupy vacancies related to the origin of the Z 12 center. The prediction based on the proposed analytical model is mostly valid for SiC after oxidation at any temperature, for any oxidation time, and any initial Z 12-concentration. Based on the results, the authors experimentally achieved the elimination of the Z 12 center to a depth of about 90 μm in the sample with a relatively high initial-Z 12-concentration of 10 13 cm -3 by thermal oxidation at 1400°C for 16.5 h. Furthermore, prediction of carrier lifetimes in SiC from the Z 12 profiles was realized through calculation based on a diffusion equation, which considers excited-carrier diffusion and recombination in the epilayer, in the substrate, and at the surface. © 2012 American Institute of Physics.

    DOI: 10.1063/1.3692766

    Web of Science

    Scopus

  134. High temperature annealing of n-type 4H-SiC: Impact on intrinsic defects and carrier lifetime

    Zippelius Bernd, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 111 ( 3 )   2012.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    In this paper, the impact of high-temperature annealing of 4H silicon carbide (SiC) on the formation of intrinsic defects, such as Z 1/2 and EH 6/7, and on carrier lifetimes was studied. Four nitrogen-doped epitaxial layers with various initial concentrations of the Z 1/2- and EH 6/7-centers (10 11 - 10 14 cm -3) were investigated by means of deep level transient spectroscopy and microwave photoconductance decay. It turned out that the high-temperature annealing leads to a monotone increase of the Z 1/2- and EH 6/7- concentration starting at temperatures between 1600°C and 1750°C, depending on the initial defect concentration. In the case of samples with high initial defect concentration (10 14 cm -3) a distinct decrease in Z 1/2- and EH 6/7-concentration in the temperature range from 1600°C to 1750°C was observed, being consistent with previous reports. For higher annealing temperatures (T anneal 1750°C), the defect concentration is independent of the samples' initial values. As a consequence, beside the growth conditions, such as C/Si ratio, the thermal post-growth processing has a severe impact on carrier lifetimes, which are strongly reduced for samples annealed at high temperatures. © 2012 American Institute of Physics.

    DOI: 10.1063/1.3681806

    Web of Science

    Scopus

  135. Growth of Nitrogen-Polar 2H-AlN on Step-Height-Controlled 6H-SiC(000(1)over-bar) Substrate by Molecular-Beam Epitaxy

    Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 51 ( 2 )   2012.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    200-nm-thick N-polar AlN layers were grown on 6H-SiC(0001̄) substrates with 6-bilayer-high steps by molecular-beam epitaxy. During N-polar AlN growth, multinucleation growth occured easily, increasing the surface roughness of AlN. By reducing supersaturation (nucleation probability), the surface roughness was improved. The FWHMs of (0002) and (011̄2̄) ω-scan diffraction peaks of the AlN layer were 120 and 210 arcsec, respectively. The formation of stacking-mismatch boundaries (SMBs) was successfully suppressed by step-height control of the SiC substrate and the initial layer-by-layer growth. Most of the threading dislocations (TDs) were generated at the step edges of the SiC surfaces. The density of TDs in the AlN layers was 2 × 10 9 cm -2. © 2012 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.51.02BH02

    Web of Science

    Scopus

  136. Space-modulated junction termination extension for ultrahigh-voltage p-i-n diodes in 4H-SiC

    Feng G., Suda J., Kimoto T.

    IEEE Transactions on Electron Devices   Vol. 59 ( 2 ) page: 414 - 418   2012.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    An edge termination method, referred to as space-modulated junction termination extension (SMJTE) combined with a mesa structure, is presented for ultrahigh-voltage p-i-n diodes in 4H-SiC. Numerical device simulations have been performed for over 15-kV-class 4H-SiC p-i-n diodes with the proposed edge termination. The structure exhibits a high breakdown capability with an improved tolerance for the deviation of impurity dose in the JTE region. Unlike conventional multi-implantation, the proposed termination technique utilizes a single-step implantation with a single mask. A desired laterally tapered doping profile is achieved by fragmenting a conventional JTE region using relatively wide spaces. The simple process of the proposed edge termination makes it applicable to fabrication of various high-voltage devices in 4H-SiC. © 2006 IEEE.

    DOI: 10.1109/TED.2011.2175486

    Scopus

  137. Breakdown Characteristics of 12-20 kV-class 4H-SiC PiN Diodes with Improved Junction Termination Structures

    Niwa Hiroki, Feng Gan, Suda Jun, Kimoto Tsunenobu

    2012 24TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD)     page: 381 - 384   2012

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  138. Defect Electronics in SiC and Fabrication of Ultrahigh-Voltage Bipolar Devices

    Kimoto T., Suda J., Feng G., Miyake H., Kawahara K., Niwa H., Okuda T., Ichikawa S., Nishi Y.

    GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 2   Vol. 50 ( 3 ) page: 25 - 35   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:ECS Transactions  

    Fast epitaxial growth, defect reduction, device designing, and process development in SiC toward ultrahigh-voltage (> 10 kV) bipolar devices are investigated. 100∼200μ-thick 4H-SiC epilayers with a low background doping concentration in the low 1013 cm-3 can be grown at a growth rate greater than 50μ/h. Impacts of extended defects on carrier recombination are clarified in photoluminescence mapping measurements. Generation and reduction of Z1/2 center, the dominant lifetime killer, are summarized. After Z1/2 elimination by thermal oxidation at 1400°C, the carrier lifetime can be enhanced to 25 s or even longer. By utilizing space-modulated junction termination extension, a 21.7 kV PiN diode is demonstrated. Through unique process development, the current gain in bipolar junction transistors is increased to 250∼330. © The Electrochemical Society.

    DOI: 10.1149/05003.0025ecst

    Web of Science

    Scopus

  139. Doping-Induced Lattice Mismatch and Misorientation in 4H-SiC Crystals

    Sasaki S., Suda J., Kimoto T.

    SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2   Vol. 717-720   page: 481 - 484   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    The c- and a-lattice constants of nitrogen-doped 4H-SiC were measured in the wide temperature range (RT - 1100°C). The samples used in this study were heavily doped substrates and lightly-doped free-standing epilayers. The lattice constants at room temperature are almost identical for all the samples. However, the lattice contraction by heavy nitrogen doping was clearly observed at high temperatures, which indicates that the thermal expansion coefficients are dependent on the nitrogen concentration. The lattice mismatch (Δd/d) between a lightly-doped free-standing epilayer (Nd = 6×10 14 cm-3) and a heavily-doped substrate (Nd = 2×1019 cm-3) was calculated as 1.7×10 -4 at 1100°C. The authors also investigated lattice constants of high-dose N+, P+, and Al+-implanted 4H-SiC. Reciprocal space mapping (RSM) was utilized to investigate the lattice mismatch and misorientation. The RSM images show the c-lattice expansion and c-axis tilt of the ion-implanted layers, irrespective of ion species. The authors conclude that the lattice expansion is not caused by heavy doping itself, but by secondary defects formed after the ion-implantation and activation-annealing process. © (2012) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.717-720.481

    Web of Science

    Scopus

  140. Experimental Study on Various Junction Termination Structures Applied to 15 kV 4H-SiC PiN Diodes

    Niwa Hiroki, Feng Gan, Suda Jun, Kimoto Tsunenobu

    SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2   Vol. 717-720   page: 973 - 976   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    Breakdown characteristics of 4H-SiC PiN diodes with various JTE structures have been investigated. By combining two-zone JTE and Space-Modulated JTE (SM-JTE), a breakdown voltage over 15 kV, corresponding to about 93 % of the parallel-plane breakdown voltage, was realized. The window of optimum JTE dose to obtain high breakdown voltage was widened, which indicates the robustness to the deviation of JTE dose. By comparing the breakdown voltage obtained by simulation and experimental results, impacts of the charge near the SiO 2/SiC interface are discussed. © (2012) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.717-720.973

    Web of Science

    Scopus

  141. Enhanced Current Gain (> 250) in 4H-SiC Bipolar Junction Transistors by A Deep-Level-Reduction Process

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2   Vol. 717-720   page: 1117 - 1122   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    We demonstrate 4H-SiC bipolar junction transistors (BJTs) with an enhanced current gain over 250. High current gain was achieved by utilizing optimized device geometry as well as optimized surface passivation, continuous epitaxial growth of the emitter-base junction, combined with an intentional deep-level-reduction process based on thermal oxidation to improve the lifetime in p-SiC base. We achieved a maximum current gain (β) of 257 at room temperature and 127 at 250°C for 4H-SiC BJTs fabricated on the (0001)Si-face. The gain of 257 is twice as large as the previous record gain. We also demonstrate BJTs on the (000-1)C-face that showed the highest β of 439 among the SiC BJTs ever reported. © (2012) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.717-720.1117

    Web of Science

    Scopus

  142. Elimination of Deep Levels in Thick SiC Epilayers by Thermal Oxidation and Proposal of the Analytical Model

    Kawahara Koutarou, Suda Jun, Kimoto Tsunenobu

    SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2   Vol. 717-720   page: 241 - 246   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    It has been clarified that the Z1/2 center, a well known deep level as a lifetime killer, can be reduced to the concentration below 10 11 cm-3 by thermal oxidation or C+ implantation plus Ar annealing. In this study, the authors investigate the trap-reduction phenomena systematically (experimentally), and propose a model to analyze the phenomena. Furthermore, prediction of the defect distributions is realized by solving a diffusion equation in accordance with the trap reduction model. This analytical model can explain almost all experimental data: oxidation-temperature dependence, oxidation-time dependence, and initial-Z1/2- concentration dependence of the defect reduction. Based on these results, the authors achieved the elimination of the Z1/2 center to a depth of ∼100 μm in a sample with a relatively high initial-Z1/2- concentration of 1013 cm-3 by thermal oxidation at 1400°C for 16.5 h. © (2012) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.717-720.241

    Web of Science

    Scopus

  143. On the Formation of Intrinsic Defects in 4H-SiC by High Temperature Annealing Steps

    Zippelius B., Suda J., Kimoto T.

    SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2   Vol. 717-720   page: 247 - 250   2012

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    In this paper the impact of high temperature annealing on the formation of intrinsic defects in 4H-SiC such as Z1/2 and EH6/7 is examined. Three epitaxial layers with various initial concentrations of the Z1/2- and EH6/7-centers (1011 - 1013 cm-3) are investigated by means of deep level transient spectroscopy (DLTS). It turns out that depending on the initial defect concentration, the high temperature annealing leads to a monotonic increase of the Z1/2- and EH6/7-concentration in a temperature range from 1600 to 1750°C. For higher temperatures, the resulting defect concentration is independent of the sample's initial values. Therefore, beside the growth conditions such as C/Si ratio, the thermal post-growth processing has a severe impact on the carrier lifetime and must be taken into account during device fabrication. © (2012) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.717-720.247

    Web of Science

    Scopus

  144. 4H-SiC bipolar junction transistors with record current gains of 257 on (0001) and 335 on (000-1)

    Miyake H., Kimoto T., Suda J.

    Proceedings of the International Symposium on Power Semiconductor Devices and ICs     page: 292 - 295   2011.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of the International Symposium on Power Semiconductor Devices and ICs  

    We demonstrate 4H-SiC bipolar junction transistors (BJTs) with record current gains. Improved current gain was achieved by utilizing optimized device geometry as well as optimized surface passivation and continuous epitaxial growth of the emitter-base junction, combined with an intentional deep-level-reduction process based on thermal oxidation to improve the lifetime in p-SiC base. Current gain (β) of 257 was achieved for 4H-SiC BJTs fabricated on the (0001)Si-face. The gain of 257 is twice as large as the previous record gain. We also demonstrate, for the first time, BJTs on the (000-1)C-face that showed the highest β of 335 among the SiC BJTs ever reported. © 2011 IEEE.

    DOI: 10.1109/ISPSD.2011.5890848

    Scopus

  145. Epitaxial growth and defect control of SiC for high-voltage power devices

    Kimoto T., Suda J.

    Journal of the Vacuum Society of Japan   Vol. 54 ( 6 ) page: 362 - 368   2011.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of the Vacuum Society of Japan  

    Recent progress in fast epitaxial growth and defect control of silicon carbide (SiC) toward development of high-voltage power devices is reviewed. In chemical vapor deposition of 4H-SiC on off-axis (0001), a high growth rate of 85 μm/h and a low background doping of 1 × 10 13 cm -3 are achieved. Conversion of basal-plane dislocations to threading edge dislocations and generation of stacking faults during epitaxial growth are discussed. Deep levels in as-grown n-type and p-type 4H-SiC epitaxial layers have been investigated. A lifetime-killing defect, Z 1/2 center, can be almost eliminated by thermal oxidation, which leads to significant increase in carrier lifetimes. The obtained carrier lifetimes are long enough to fabricate 10 kV-class bipolar devices. Control of carrier lifetimes by lowenergy electron irradiation is demonstrated.

    DOI: 10.3131/jvsj2.54.362

    Scopus

  146. Reliability of nitrided gate oxides for N- and P-type 4H-SiC(0001) metal-oxide-semiconductor devices

    Noborio M., Grieb M., Bauer A.J., Peters D., Friedrichs P., Suda J., Kimoto T.

    Japanese Journal of Applied Physics   Vol. 50 ( 9 PART 1 )   2011.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    In this paper, we have investigated reliability of n- and p-type 4H-SiC(0001) metal-oxide-semiconductor (MOS) devices with N2O-grown oxides and deposited oxides annealed in N2O. From the results of time-dependent dielectric breakdown (TDDB) tests, it is revealed that the N 2O-grown oxides have relatively-high reliability (4-30Ccm -2 for n- and p-MOS structures). In addition, the deposited SiO 2 on n- and p-SiC exhibited a high charge-to-breakdown of 70.0 and 54.9Ccm-2, respectively. The n/p-MOS structures with the deposited SiO2 maintained a high charge-tobreakdown of 19.9/15.1Ccm -2 even at 200 °C. The deposited SiO2 annealed in N2O has promise as the gate insulator for n- and p-channel 4HSiC(0001) MOS devices because of its high charge-to-breakdown and good interface properties. © 2011 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.50.090201

    Scopus

  147. Nonradiative recombination at threading dislocations in 4H-SiC epilayers studied by micro-photoluminescence mapping

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 110 ( 3 )   2011.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Threading dislocations (TDs) in 4H-SiC epilayers have been investigated by means of micro-photoluminescence (-PL) mapping at room temperature. Enhanced nonradiative recombination at TDs was confirmed experimentally, resulting in a reduced local PL emission intensity in the -PL intensity map performed at 390 nm (near band-edge emission). The behavior of nonradiative recombination at TDs depends on the dislocation type: the screw type of TDs shows stronger effect on the nonradiative recombination activity than the edge type, evidencing a larger local reduction of PL emission intensity. Furthermore, the contrast of TDs in the μ-PL intensity map greatly depends on the carrier lifetimes of the 4H-SiC epilayers. Lifetimes longer than 0.5 s are essential to obtain a discernible contrast for the individual TDs. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3622336

    Web of Science

    Scopus

  148. 4H-SiC BJTs With Record Current Gains of 257 on (0001) and 335 on (0001)

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 32 ( 7 ) page: 841 - 843   2011.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    We demonstrate 4H-SiC bipolar junction transistors (BJTs) with record current gains. An improved current gain was achieved by utilizing optimized device geometry and continuous epitaxial growth of the emitterbase junction, combined with an intentional deep-level-reduction process based on thermal oxidation to improve the lifetime in p-SiC base. A current gain (β) of 257 was achieved for 4H-SiC BJTs fabricated on the (0001) Si face. A gain of 257 is twice as large as the previous record gain. We also demonstrate BJTs on the (0001) C face that showed the highest β of 335 among the SiC BJTs ever reported. © 2011 IEEE.

    DOI: 10.1109/LED.2011.2142291

    Web of Science

    Scopus

  149. Anomalously low Ga incorporation in high Al-content AlGaN grown on (11(2)over-bar0) non-polar plane by molecular beam epitaxy

    Ueta Shunsaku, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 208 ( 7 ) page: 1498 - 1500   2011.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (A) Applications and Materials Science  

    Crystalline orientation dependence of Ga incorporation in growth of high Al-content AlGaN was investigated. Growth was carried out by molecular-beam epitaxy (MBE) using elemental Al, Ga, and rf-plasma-excited nitrogen under various V/III ratios. 6H-SiC (0001), 4H-SiC (1√100) and 4H-SiC (11√20) were used as substrates. Ga incorporation increased with increase of V/III ratio in the layers grown on (0001) and (1√100) planes. On the other hand, Ga was not incorporated in the layer grown on (11√20) plane even when the layer was grown under a nitrogen rich condition, indicating much lower Ga incorporation on (11√20) plane than those of other planes. AlGaN with good quality was successfully grown on (1√100) plane. Utilization of (1√100) plane is suitable in MBE growth of AlGaN-based deep-ultraviolet light emitting devices. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssa.201001033

    Web of Science

    Scopus

  150. Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers

    Hayashi T., Asano K., Suda J., Kimoto T.

    Journal of Applied Physics   Vol. 109 ( 11 )   2011.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers are investigated. The authors reported that the carrier lifetime in n-type epilayers increased by reduction of deep levels through thermal oxidation and thermal annealing. However, the carrier lifetimes in p-type epilayers were not significantly enhanced. In this study, in order to investigate the influence of surface passivation on the carrier lifetimes, the epilayer surface was passivated by different oxidation techniques. While the improvement of the carrier lifetime in n-type epilayers was small, the carrier lifetime in p-type epilayers were remarkably improved by appropriate surface passivation. For instance, the carrier lifetime was improved from 1.4 s to 2.6 s by passivation with deposited SiO2 annealed in NO. From these results, it was revealed that surface recombination is a limiting factor of carrier lifetimes in p-type 4H-SiC epilayers. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3583657

    Scopus

  151. Lifetime-Killing Defects in 4H-SiC Epilayers and Lifetime Control by Low-Energy Electron Irradiation

    Kimoto T.

    Silicon Carbide   Vol. 1   page: 267 - 286   2011.4

     More details

    Publishing type:Research paper (scientific journal)   Publisher:Silicon Carbide  

    DOI: 10.1002/9783527629053.ch10

    Scopus

  152. 4H-SiC MISFETs with Nitrogen-Containing Insulators

    Noborio M.

    Silicon Carbide   Vol. 2   page: 235 - 265   2011.3

     More details

    Publishing type:Research paper (scientific journal)   Publisher:Silicon Carbide  

    DOI: 10.1002/9783527629077.ch10

    Scopus

  153. Bandgap shift by quantum confinement effect in < 100 > Si-nanowires derived from threshold-voltage shift of fabricated metal-oxide-semiconductor field effect transistors and theoretical calculations

    Yoshioka Hironori, Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 109 ( 6 )   2011.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Si-nanowire (Si-NW) MOSFETs, the cross-sectional size (square root of the cross-sectional area of NWs) of which was changed from 18 to 4 nm, were fabricated and characterized. Both n- and p-channel MOSFETs have shown a nearly ideal subthreshold swing of 63 mV/decade. The threshold voltage of n-/p-channel MOSFETs has gradually increased/decreased with decreasing the cross-sectional size. The bandgap shift from bulk Si has been derived from the threshold-voltage shift. The bandgap of Si-NWs was calculated by a density functional theory, tight binding method, and effective mass approximation. The calculated bandgap shows good agreement with that derived from threshold voltage. The theoretical calculation indicates that the bandgap is dominated by the cross-sectional size (area) and is not very sensitive to the shape within the aspect-ratio range of 1.0-2.5. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3559265

    Web of Science

    Scopus

  154. Quantum-confinement effect on holes in silicon nanowires: Relationship between wave function and band structure

    Morioka Naoya, Yoshioka Hironori, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 109 ( 6 )   2011.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The authors theoretically studied the valence band structure and hole effective mass of rectangular cross-sectional Si nanowires (NWs) with the crystal orientation of [110], [111], and [001]. The E-k dispersion and the wave function were calculated using an sp3d5s tight-binding method and analyzed with the focus on the nature of p orbitals constituting the subbands. In [110] and [111] nanowires, longitudinal/transverse p orbitals are well separated and longitudinal component makes light (top) subbands and transverse component makes heavy subbands. The heavy subbands are located far below the top light band when NW has square cross-section, but they gain their energy with the increase in the NW width and come near the band edge. This energy shift of heavy bands in [110] NWs shows strong anisotropy to the direction of quantum confinement whereas that in [111] NWs does not have such anisotropy. This anisotropic behavior and the difference among orientations are understandable by the character of the wave function of heavy subbands. Regarding the [001] nanowires, the top valence state is formed by the mixture of longitudinal/transverse p orbitals, which results in heavy effective mass and large susceptibility to lateral-size variation. The correlation of the wave function of hole states between nanowires and bulk is also discussed briefly. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3552593

    Web of Science

    Scopus

  155. Improvement of Current Gain in 4H-SiC BJTs by Surface Passivation With Deposited Oxides Nitrided in N2O or NO

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 32 ( 3 ) page: 285 - 287   2011.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    We report the improvement of current gain in 4H-SiC bipolar junction transistors (BJTs) by utilizing deposited oxides as a surface passivation layer. Various postdeposition annealing processes, including annealing ambient (N 2, N2O, and NO) and annealing time, were investigated. We successfully demonstrate SiC BJTs with high current gains β of 73 and 102 using deposited oxides annealed in N2O and NO, respectively, whereas BJTs having conventional thermally grown oxides showed a current gain of 50. © 2006 IEEE.

    DOI: 10.1109/LED.2010.2101575

    Web of Science

    Scopus

  156. Origin of Etch Hillocks Formed on On-Axis SiC(000(1)over-bar) Surfaces by Molten KOH Etching

    Suda Jun, Shoji Haruki, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 50 ( 3 )   2011.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Molten KOH etching of 6H- and 4H-SiC{0001} on-axis substrates was investigated. After molten KOH etching, etch pits originating from threading dislocations (TDs) and basal-plane dislocations (BPDs) were observed on (0001) surfaces. On the other hand, large and small hillocks were observed on (0001̄) surfaces. The etch hillocks consist of SiC, indicating slower etching at TDs. By comparing the (0001) side and (0001̄) side of the same substrate, it was found that large hillocks correspond to edge-type TDs, while small hillocks correspond to screw-type TDs. © 2011 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.50.038002

    Web of Science

    Scopus

  157. Reduction of Threading Dislocation Density in 2H-AlN Grown on 6H-SiC(0001) by Minimizing Unintentional Active-Nitrogen Exposure before Growth

    Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 4 ( 2 )   2011.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    300-nm-thick AlN layers were grown directly on 6H-SiC(0001) with six Si-C bilayer-height (1.5 nm) steps by rf-plasma-assisted molecular-beam epitaxy (MBE). To avoid unintentional active-nitrogen exposure, AlN was grown just after the nitrogen plasma ignition. By combining optimized Ga pre-deposition and no active-nitrogen exposure, layer-by-layer growth was realized from the first layer of AlN. Screw-type and edge-type threading dislocation densities in the AlN layer were reduced to 6 × 104 and 4 × 108 cm-2, respectively. Most of the edge-type dislocations were located at the step edge of the SiC substrate. The dislocation density of the AlN grown on the terrace of the SiC substrate was as low as 8 × 107 cm-2. © 2011 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.4.025502

    Web of Science

    Scopus

  158. Temperature and injection level dependencies and impact of thermal oxidation on carrier lifetimes in p-type and n-type 4H-SiC epilayers

    Hayashi T., Asano K., Suda J., Kimoto T.

    Journal of Applied Physics   Vol. 109 ( 1 )   2011.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Dependencies of temperature and injection level on carrier lifetimes in 50 μm thick p-type and n-type 4H-SiC epilayers have been investigated. The carrier lifetimes have been measured by differential microwave photoconductance decay measurements at various injection levels and temperatures. In both p-type and n-type epilayers, the carrier lifetimes gradually increased with increasing the injection level, which were naturally expected from the Shockley-Read-Hall (SRH) model, and after taking a maximum, the lifetimes dropped at the very high-injection level. In contrast, the carrier lifetimes exhibited continuous increase with elevating the temperature for both epilayers. In addition, the impact of thermal oxidation process on the carrier lifetimes has been also investigated. The thermal oxidation process, by which the Z1/2 and EH6/7 centers were remarkably reduced that had been observed in n-type 4H-SiC in our previous work, led to the improvement of the carrier lifetimes especially for n-type epilayers. The carrier lifetime reached 4.1 μs in p-type and 6.1 μs in n-type epilayers at 250 °C with an injection level of 1.8×1016 cm-3 through the thermal oxidation processing. © 2011 American Institute of Physics.

    DOI: 10.1063/1.3524266

    Scopus

  159. 4H-SiC Bipolar Junction Transistors with Record Current Gains of 257 on (0001) and 335 on (000-1)

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    2011 IEEE 23RD INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD)     page: 292 - 295   2011

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  160. Fabrication of Electrostatic-actuated Single-crystalline 4H-SiC Bridge Structures by Photoelectrochemical Etching

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    MICROMACHINING AND MICROFABRICATION PROCESS TECHNOLOGY XVI   Vol. 7926   2011

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of SPIE - The International Society for Optical Engineering  

    An electrostatic-actuated suspended bridge structure composed by single-crystalline silicon carbide (SiC) is fabricated. The structure is entirely made of homoepitaxially grown single-crystalline 4H-SiC. Electrical isolation between the suspended bridge and the base plate is established with a pnp junction formed by multiple ion implantation. The structure is fabricated by a combination of reactive ion etching (RIE) and doping-selective photoelectrochemical (PEC) etching. The suspended bridge is actuated by applying a voltage between the bridge and the base plate.

    DOI: 10.1117/12.874543

    Web of Science

    Scopus

  161. Thermo-optic Coefficients of SiC, GaN, and AlN up to 512 degrees C from Infrared to Ultraviolet Region for Tunable Filter Applications

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    MICROMACHINING AND MICROFABRICATION PROCESS TECHNOLOGY XVI   Vol. 7926   2011

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Proceedings of SPIE - The International Society for Optical Engineering  

    The temperature dependence of the refractive indices of 4H-SiC, GaN, and AlN were investigated in a wavelength range from the near band edge (392 nm for SiC, 367 nm for GaN, and 217 nm for AlN) to infrared (1700 nm) and a temperature range from room temperature to 512°C. Optical interference measurements with vertical incident configuration were employed to precisely evaluate ordinary refractive indices. In visible region, the thermo-optic coefficient of GaN has the largest value in these materials. Optical simulation of GaN-based tunable band-pass filter with AlGaN/GaN distributed Bragg reflectors (DBRs) was also carried out by using the obtained thermo-optic coefficients. It revealed that 9 nm red-shift can be obtained from room temperature to 500°C.

    DOI: 10.1117/12.874531

    Web of Science

    Scopus

  162. Tight-binding study of size and geometric effects on hole effective mass of silicon nanowires

    Moriokaa N., Yoshioka H., Suda J., Kimoto T.

    2010 Silicon Nanoelectronics Workshop, SNW 2010     2010.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:2010 Silicon Nanoelectronics Workshop, SNW 2010  

    The present tight-binding study of rectangular SiNWs along [001], [110], and [111] revealed that the hole m* of [001] and [110] NWs on the {001} basal face has strong dependence on the width. Because this nature may make the design of devices difficult, these NWs are considered to be unfavorable for p-channel devices. In contrast, rectangular [111] NWs on both (112̄) and (1̄10) basal faces are favorable for p-channel devices because they have the smallest hole m* and its value is very resistant to the variability of the width.

    DOI: 10.1109/SNW.2010.5562567

    Scopus

  163. Impacts of recombination at the surface and in the substrate on carrier lifetimes of n-type 4H-SiC epilayers

    Kimoto Tsunenobu, Hiyoshi Toru, Hayashi Toshihiko, Suda Jun

    JOURNAL OF APPLIED PHYSICS   Vol. 108 ( 8 )   2010.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    After remarkable reduction in the Z1/2 center in n-type 4H-SiC epilayers, the measured carrier lifetimes can be severely affected by other recombination paths. Impacts of carrier recombination at the surface as well as in the substrate are investigated in detail by using numerical simulation based on a diffusion equation. The simulation reveals that a very thick (>100 μm) epilayer is required for accurate measurement of carrier lifetimes if the bulk lifetime in the epilayer is longer than several microsecond, due to the extremely short lifetimes in the substrate. The fast decay often observed at the initial stage of decay curves can be explained by fast recombination at the surface and in the substrate. In experiments, the carrier lifetime is improved from 0.69 to 9.5 μs by reducing the Z1/2 center via two-step thermal treatment (thermal oxidation and Ar annealing) for a 148-μm -thick n-type epilayer. This lifetime must be still, to large extent, affected by the recombination at the surface and in the substrate, and the real bulk lifetime may be much longer. The carrier recombination paths and their impacts on the decay curves are discussed. © 2010 American Institute of Physics.

    DOI: 10.1063/1.3498818

    Web of Science

    Scopus

  164. Accurate measurement of quadratic nonlinear-optical coefficients of gallium nitride

    Abe M., Sato H., Shoji I., Suda J., Yoshimura M., Kitaoka Y., Mori Y., Kondo T.

    Journal of the Optical Society of America B: Optical Physics   Vol. 27 ( 10 ) page: 2026 - 2034   2010.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of the Optical Society of America B: Optical Physics  

    We have determined all the three independent components of quadratic nonlinear-optical coefficients of GaN by highly accurate Maker-fringe measurements on high-quality bulk samples combined with theoretical analysis taking account of the multiple-reflection effects in slightly misoriented optically anisotropic samples. Especially, the d33 coefficient is determined with sufficient accuracies for the first time, to our knowledge, by using (112̄0)-oriented samples. The obtained values of quadratic nonlinear-optical coefficients are d31 =2.5±0.1 pm/V, d 15=2.5±0.1 pm/V, and d33=-3.8±0.2 pm/V at the fundamental wavelength of 1.064 μm. © 2010 Optical Society of America.

    DOI: 10.1364/JOSAB.27.002026

    Scopus

  165. Nearly ideal current-voltage characteristics of schottky barrier diodes formed on hydride-vapor-phase-epitaxy-grown GaN free-standing substrates

    Suda J., Yamaji K., Hayashi Y., Kimoto T., Shimoyama K., Namita H., Nagao S.

    Applied Physics Express   Vol. 3 ( 10 )   2010.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The current-voltage characteristics of Schottky barrier diodes formed on GaN(0001) free-standing substrates with net donor concentrations of 7:6 × 1015-1:4 × 1017 cm-3 are discussed. The substrates were grown by hydride vapor phase epitaxy. Ni Schottky contacts were directly formed on chemical-mechanical-polished Ga-polar faces of the substrates. Nearly ideal characteristics for both directions were obtained. The ideality factors for forward characteristics are 1.02 -1.05, very close to unity. The reverse characteristics agree well with calculations based on thermionicfield emission theory without any fitting parameter. © 2010 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.3.101003

    Scopus

  166. Demonstration of Common-Emitter Operation in AlGaN/SiC Heterojunction Bipolar Transistors

    Miyake Hiroki, Kimoto Tsunenobu, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 31 ( 9 ) page: 942 - 944   2010.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    We report here on the fabrication and characterization of new aluminum gallium nitride (AlGaN)/silicon carbide heterojunction bipolar transistors (HBTs). In the HBTs, AlN/GaN short-period superlattice (quasi-AlGaN) was employed as the widegap emitter. We have successfully demonstrated band-offset control and the first commonemitter-mode operation (β ∼ 2.7) in the HBTs. © 2010 IEEE.

    DOI: 10.1109/LED.2010.2052012

    Web of Science

    Scopus

  167. Reduction of deep levels generated by ion implantation into n-and p-type 4H-SiC

    Kawahara K., Suda J., Pensl G., Kimoto T.

    Journal of Applied Physics   Vol. 108 ( 3 )   2010.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The authors have investigated effects of thermal oxidation on deep levels in the whole energy range of the band gap of 4H-SiC by deep level transient spectroscopy. The deep levels are generated by ion implantation. The dominant defects in n-type samples after ion implantation and high-temperature annealing at 1700 °C are IN3 (Z1/2: EC-0.63 eV) and IN9 (EH 6/7: EC-1.5 eV) in low-dose-implanted samples, and IN8 (EC-1.2 eV) in high-dose-implanted samples. These defects can remarkably be reduced by thermal oxidation at 1150 °C. In p-type samples, however, IP8 (HK4: EV +1.4 eV) survives and additional defects such as IP4 (HK0: EV +0.72 eV) appear after thermal oxidation in low-dose-implanted samples. In high-dose-implanted p-type samples, three dominant levels, IP5 (HK2: EV +0.85 eV), IP6 (EV +1.0 eV), and IP7 (HK3: EV +1.3 eV), are remarkably reduced by oxidation at 1150 °C. The dominant defect IP4 observed in p-type 4H-SiC after thermal oxidation can be reduced by subsequent annealing in Ar at 1400 °C. These phenomena are explained by a model that excess interstitials are generated at the oxidizing interface, which diffuse into the bulk region. © 2010 American Institute of Physics.

    DOI: 10.1063/1.3456159

    Scopus

  168. Sources of Epitaxial Growth-Induced Stacking Faults in 4H-SiC

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF ELECTRONIC MATERIALS   Vol. 39 ( 8 ) page: 1166 - 1169   2010.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Electronic Materials  

    Successive reactive-ion etching and microphotoluminescence (PL) intensity mapping have been performed in order to investigate the sources of epitaxial growth-induced stacking faults (SFs) in thick 4H-SiC epilayers. Three kinds of SFs, i.e., 4SSFs, 3SSFs, and 2SSFs, have been identified in the samples. Two of these (3SSFs and 2SSFs) show similar nucleation behaviors, and their formation may be due to stress within the epitaxial layer. In contrast, 4SSFs nucleate at the epilayer-substrate interface and might be related to an unknown dislocation, which shows a rounded-shape etch pit in the substrate. © 2010 TMS.

    DOI: 10.1007/s11664-010-1192-6

    Web of Science

    Scopus

  169. Deep levels induced by reactive ion etching in n- and p-type 4H-SiC

    Kawahara K., Krieger M., Suda J., Kimoto T.

    Journal of Applied Physics   Vol. 108 ( 2 )   2010.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    In this study, the authors investigate deep levels, which are induced by reactive ion etching (RIE) of n-type/p-type 4H-SiC, by deep level transient spectroscopy (DLTS). The capacitance of a Schottky contact fabricated on as-etched p-type SiC is abnormally small due to compensation or deactivation of acceptors extending to a depth of ∼14 μm, which is nearly equal to the epilayer thickness. The value of the capacitance can recover to that of a Schottky contact on as-grown samples after annealing at 1000 °C. However, various kinds of defects, IN2 (EC-0.30 eV), EN (EC -1.6 eV), IP1 (EV +0.30 eV), IP2 (EV +0.39 eV), IP4 (HK0: EV +0.72 eV), IP5 (EV +0.85 eV), IP7 (EV +1.3 eV), and EP (EV +1.4 eV), remain at a high concentration (average of total defect concentration in the region ranging from 0.3 μm to 1.0 μm:∼5× 1014 cm-3) even after annealing at 1000 °C. The concentration of all these defects generated by RIE, except for the IP4 (HK0) center, remarkably decreases by thermal oxidation. In addition, the HK0 center can also be reduced significantly by a subsequent annealing at 1400 °C in Ar. © 2010 American Institute of Physics.

    DOI: 10.1063/1.3460636

    Scopus

  170. Electrical characterization and reliability of nitrided-gate insulators for N- and P-Type 4H-SiC MIS devices

    Noborio M., Grieb M., Bauer A.J., Peters D., Friedrichs P., Suda J., Kimoto T.

    Materials Science Forum   Vol. 645-648   page: 825 - 828   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    In this paper, nitrided insulators such as N2O-grown oxides, deposited SiO2 annealed in N2O, and deposited SiN x/SiO2 annealed in N2O on thin-thermal oxides have been investigated for realization of high performance n- and p-type 4H-SiC MIS devices. The MIS capacitors were utilized to evaluate MIS interface characteristics and the insulator reliability. The channel mobility was determined by using the characteristics of planar MISFETs. Although the N 2O-grown oxides are superior to the dry O2-grown oxides, the deposited SiO2 and the deposited SiNx/SiO2 exhibited lower interface state density (n-MIS: below 7×1011 cm-2eV-1 at EC-0.2 eV, p-MIS: below 6×1011 cm-2eV-1 at EV+0.2 eV) and higher channel mobility (n-MIS: over 25 cm2/Vs, p-MIS: over 10 cm2/Vs). In terms of reliability, the deposited SiO2 annealed in N2O exhibits a high charge-to-breakdown over 50 C/cm 2 at room temperature and 15 C/cm2 at 200°C. The nitrided-gate insulators formed by deposition method have superior characteristics than the thermal oxides grown in N2O. © (2010) Trans Tech Publications, Switzerland.

    DOI: 10.4028/www.scientific.net/MSF.645-648.825

    Scopus

  171. Enhancement of initial layer-by-layer growth and reduction of threading dislocation density by optimized Ga pre-irradiation in molecular-beam epitaxy of 2H-AlN on 6H-SiC (0001)

    Okumura Hironori, Kimoto Tsunenobu, Suda Jun

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 7, NO 7-8   Vol. 7 ( 7-8 ) page: 2094 - 2096   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (C) Current Topics in Solid State Physics  

    300-nm-thick AlN layers without a nucleation layer were grown on 6H-SiC (0001) vicinal substrates with 3-bilayer-height steps by rf-plasma-assisted molecular-beam epitaxy. A Ga beam was supplied for 0 to 30 seconds just before growth of AlN. The Ga pre-irradiation for 7 seconds (~1.6 ML) was found to be effective for realization of the AlN layer-by-layer growth mode at an earlier stage of the growth and reduction of threading dislocation densities (TDD) in the AlN layers. The screw-type and edge-type TDDs were ∼106 cm-2 and 6×108 cm-2, respectively. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

    DOI: 10.1002/pssc.200983579

    Web of Science

    Scopus

  172. Enhancement of Carrier Lifetimes in n-Type 4H-SiC Epitaxial Layers by Improved Surface Passivation

    Kimoto Tsunenobu, Nanen Yuichiro, Hayashi Toshihiko, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 3 ( 12 )   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    Carrier lifetimes in n-type 4H-SiC epitaxial layers are limited by several factors such as deep levels, surface recombination, and recombination in the substrate. In this study, the carrier lifetime is significantly improved from 0.68 to 13.1 μs by eliminating deep levels and by improving surface passivation. Deep levels can be almost eliminated by two-step annealing as reported before, and the surface recombination can be reduced by passivating the surface with a deposited oxide annealed in nitric oxide at 1300 °C. Major recombination paths are discussed based on numerical simulation. © 2010 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.3.121201

    Web of Science

    Scopus

  173. Influence of Effective Fixed Charges on Short-Channel Effects in SiC Metal-Oxide-Semiconductor Field-Effect Transistors

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 49 ( 2 )   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Influence of effective fixed charges, which are located near the metal-oxide-semiconductor (MOS) interface, on short-channel effects in 4H-SiC MOS field-effect transistors (FETs) has been investigated. The relationship between the threshold voltage and the channel length was theoretically calculated by using an original charge-share model, which takes the effective fixed charges into account. As a result, it was revealed that the effective fixed charges, which are attributed to electron trapping at the interface states, affect the relationship. The threshold voltage is decreased by reducing the channel length in the relatively-long channel region when the effective fixed charges exist. The theoretical relationship between the threshold voltage and the channel length calculated by using the proposed model agrees very well with the experimental results. © 2010 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.49.024204

    Web of Science

    Scopus

  174. Nonpolar 4H-Polytype AlN/AlGaN Multiple Quantum Well Structure Grown on 4H-SiCd(1(1)over-bar00)

    Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 3 ( 5 )   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    Nonpolar 4H-polytype AlN/AlGaN multiple quantum well (MQW) structures were grown on 4H-SiC(11̄00) substrates by molecular-beam epitaxy. Layer-by-layer growth of MQW layers is observed and abrupt AlN/AlGaN interfaces have been achieved. Generation of additional extended defects is not observed at the AlN/AlGaN interfaces and the crystal structure of 4H-polytype is preserved throughout the entire MQW structure. In cathodoluminescence spectra, a band-edge emission peak is observed at 5.41 eV (229 nm). The band edge peak position is not blue-shifted when the irradiation beam current is increased. © 2010 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.3.051001

    Web of Science

    Scopus

  175. Nondestructive Visualization of Individual Dislocations in 4H-SiC Epilayers by Micro Photoluminescence Mapping

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 49 ( 9 )   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    Dislocations in 4H-SiC epilayers were imaged nondestructively by means of micro photoluminescence (μ-PL) mapping at room temperature. The one-to-one correspondence between the individual dislocations and the μ-PL mapping contrast has been consistently obtained. By analyzing the reduction of the intensity in the μ-PL mapping image performed at 390nm (near band-edge emission), we were able to distinguish threading screw dislocations and threading edge dislocations. Furthermore, it was found that a basal plane dislocation dissociates into a single Shockley stacking fault during the measurement. © 2010 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.49.090201

    Web of Science

    Scopus

  176. Non-destructive detection and visualization of extended defects in 4H-SiC epilayers

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    B - SILICON CARBIDE 2010-MATERIALS, PROCESSING AND DEVICES   Vol. 1246   page: 37 - 42   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Research Society Symposium Proceedings  

    The extended defects, such as dislocations and in-grown stacking faults (IGSFs), in 4H-SiC epilayers have been detected and visualized by a non-destructive method, the micro photoluminescence (μ-PL) intensity mapping method, at room temperature. The one-to-one correspondence between the extended defects and the μ-PL mapping contrast has been successfully obtained. A threading dislocation corresponds to a dark circle with the reduced intensity in the μ-PL mapping image performed at 390 nm, while a basal plane dislocation dissociates into a single Shockley SF during the measurements. Three kinds of IGSFs have been identified in the samples. Each kind of IGSF shows the distinct PL emission located at 460 nm, 480 nm, and 500 nm, respectively. The shapes and distributions of IGSFs have also been profiled by μ-PL intensity mapping. © 2010 Materials Research Society.

    DOI: 10.1557/PROC-1246-B03-02

    Web of Science

    Scopus

  177. Lifetime-killing defects in 4H-SiC epilayers and lifetime control by low-energy electron irradiation

    Kimoto Tsunenobu, Danno Katsunori, Suda Jun

    SILICON CARBIDE, VOL 1: GROWTH, DEFECTS, AND NOVEL APPLICATIONS     page: 267 - 286   2010

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  178. Temperature and injection level dependencies of carrier lifetimes in p-type and n-type 4H-SiC epilayers

    Hayashi T., Asano K., Suda J., Kimoto T.

    Materials Science Forum   Vol. 645-648   page: 199 - 202   2010

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    Temperature and injection level dependencies of carrier lifetimes in p-type and n-type 4H-SiC epilayers have been investigated. The carrier lifetimes have been measured by differential microwave photoconductance decay measurements at various injection levels and temperatures. In both p-type and n-type epilayers, the carrier lifetimes gradually increased with increasing the injection level except for the very high injection condition. And the carrier lifetimes exhibited continuous increase with elevating the temperature for both epilayers. The carrier lifetime reached 3.3 μs in p-type and 4.2 μs in n-type epilayers at 250°C and an injection level of 1.8×1016 cm-3. © (2010) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.645-648.199

    Scopus

  179. Characterization of major in-grown stacking faults in 4H-SiC epilayers

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    PHYSICA B-CONDENSED MATTER   Vol. 404 ( 23-24 ) page: 4745 - 4748   2009.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica B: Condensed Matter  

    The optical properties of major in-grown stacking faults (IGSFs) in 4H-SiC epilayers have been characterized by micro-photoluminescence (micro-PL) spectroscopy and its intensity mapping. Strong PL emissions from the IGSFs are observed even at room temperature. Three kinds of IGSFs have been identified in the samples based on the micro-PL spectra. Each kind of IGSF shows the distinct PL emission peak located at 460, 480, and 500 nm, respectively. The micro-PL intensity mapping at the emission band of each IGSF has been performed to spatially profile the IGSF. The shapes, distributions, and densities of IGSFs in the epilayers are then presented. The microstructure of each IGSF has been revealed by high-resolution transmission electron microscopy observations. The stacking sequences of three IGSFs are determined as (4,4), (3,5), and (6,0) in the Zhdanov's notation, respectively, which apparently differ from the perfect 4H-SiC, (2,2). Three identified IGSFs are then classified as quadruple Shockley SFs, triple Shockley SFs, and double Shockley SFs, respectively, based on the shear formation model. © 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2009.08.189

    Web of Science

    Scopus

  180. Demonstration of SiC heterojunction bipolar transistors with AlN/GaN short-period superlattice widegap emitter

    Miyake H., Kimoto T., Suda J.

    Device Research Conference - Conference Digest, DRC     page: 281 - 282   2009.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Device Research Conference - Conference Digest, DRC  

    SiC bipolar-junction transistors (BJTs) are attractive candidates for high-power switching devices due to their high breakdown voltage and low on-resistance. However, SiC BJT has so far suffered from the limited current gain. An alternative device structure would be heterojunction bipolar transistors (HBTs). Because it is impossible to grow SixC 1-x solid solutions with x near 0.5, HBTs cannot be fabricated within group-IV semiconductors. Heteroepitaxial growth of wider bandgap group-III nitride (Al)GaN on SiC is one possible way to realize bandgap engineering in SiC devices. The fabrication of (Al)GaN/SiC HBTs was first reported by Pankove et al. [1] followed by several groups [2]. But any HBTs did not show common-emitter mode operation due to the large leakage at the emitterjunction. © 2009 IEEE.

    DOI: 10.1109/DRC.2009.5354933

    Scopus

  181. In situ gravimetric monitoring of thermal decomposition and hydrogen etching rates of 6H-SiC(0001) Si face

    Akiyama K., Ishii Y., Abe S., Murakami H., Kumagai Y., Okumura H., Kimoto T., Suda J., Koukitu A.

    Japanese Journal of Applied Physics   Vol. 48 ( 9 Part 1 ) page: 0955051 - 0955054   2009.12

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The thermal decomposition and hydrogen etching of a 6H-SiC(0001) Si-face were directly monitored using an in situ gravimetric monitoring system. The monitoring of the weight change of the 6H-SiC Si-face using this system clarified the dependences of the thermal decomposition and hydrogen etching rates on the substrate temperature. Although the thermal decomposition of the 6H-SiC Si-face above 1400 °C generated a graphite layer since only the Si atom directly desorbs from the surface, the etching of the 6H-SiC Si-face by hydrogen did not form this layer, and both Si and C atoms react with hydrogen. Moreover, the surface reaction of the 6H-SiC Si face with H2 and the resultant surface morphology were found to change at approximately 1250 °C. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.48.095505

    Scopus

  182. Electrostatic-Actuated Suspended Ribbon Structure Fabricated in Single-Crystalline SiC by Selective Photoelectrochemical Etching

    Suda Jun, Watanabe Naoki, Fukunaga Katsuhiko, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 48 ( 11 )   2009.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    An electrostatic-actuated suspended ribbon structure composed of single-crystalline SiC is presented. All the main parts of the structure, namely, a suspended ribbon, posts, base plate, and electrical connections, are made of homoepitaxially grown single-crystalline 4H-SiC with selective ion implantations. Electrical isolation between the ribbon and the base plate is established with a pnp junction. The structure is fabricated by a combination of reactive ion etching (RIE) and doping-selective photoelectrochemical (PEC) etching. The suspended ribbon is actuated by applying a voltage between the ribbon and the base plate. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.48.111101

    Web of Science

    Scopus

  183. Enhanced Drain Current of 4H-SiC MOSFETs by Adopting a Three-Dimensional Gate Structure

    Nanen Yuichiro, Yoshioka Hironori, Noborio Masato, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 56 ( 11 ) page: 2632 - 2637   2009.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    4H-SiC (0001) metal-oxide-semiconductor field-effect transistors (MOSFETs) with a 3-D gate structure, which has a top channel on the (0001) face and side-wall channels on the {1120} face, have been fabricated. The 3-D gate structures with a 1-5-μm width and a 0.8- μm height have been formed by reactive ion etching, and the gate oxide has been deposited by plasma-enhanced chemical vapor deposition and then annealed in N2O ambient at 1300 °C. The fabricated MOSFETs have exhibited good characteristics: The ION/IOFF ratio, the subthreshold swing, and VTH are 109, 210 mV/decade, and 3.5 V, respectively. The drain current normalized by the gate width is increasing with decreasing the gate width. The normalized drain current of a 1-μm-wide MOSFET is 16 times higher than that of a conventional planar MOSFET. © 2009 IEEE.

    DOI: 10.1109/TED.2009.2030437

    Web of Science

    Scopus

  184. Accurate Measurements of second-order nonlinear optical coefficients of 6H and 4H silicon carbide

    Sato H., Abe M., Shoji I., Suda J., Kondo T.

    Journal of the Optical Society of America B: Optical Physics   Vol. 26 ( 10 ) page: 1892 - 1896   2009.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of the Optical Society of America B: Optical Physics  

    The second-order nonlinear optical coefficients of 4H-SiC and 6H-SiC have been measured by use of two second-harmonic generation methods, the rotational Maker-fringe and wedge techniques, at the fundamental wavelength of 1.064 μm. Measurements on high-quality (0001) and (112̄0) plane samples as well as rigorous analyses taking into account the multiple-reflection effects allowed us to accurately determine the magnitudes of the nonlinear optical coefficients. The obtained values are d31 = 6.7 pm/V, d15 = 6.5 pm/V, and d33 = -12.5 pm/V for 6H-SiC; and d31 = 6.5 pm/V, d15 = 6.7 pm/V, and d33 = -11.7 pm/V for 4H-SiC. © 2009 Optical Society of America.

    DOI: 10.1364/JOSAB.26.001892

    Scopus

  185. 4H-SiC MISFETs with nitrogen-containing insulators

    Noborio M., Suda J., Beljakowa S., Krieger M., Kimoto T.

    Physica Status Solidi (A) Applications and Materials Science   Vol. 206 ( 10 ) page: 2374 - 2390   2009.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (A) Applications and Materials Science  

    4H-SiC MISFETs with nitrogen-containing insulators have been fabricated and characterized. Several techniques have been explored to incorporate nitrogen in the gate insulator in order to improve the density of interface states and thereby the channel mobility. The techniques are N 2O-grown oxides, the oxidation of a surface layer co-implanted with N + and Al +, deposited SiO 2 annealed in N 2O and NO, and deposited SiN x/SiO 2 annealed in N 2O. By optimizing the formation process of the gate insulators, MIS capacitors with N-containing insulators have demonstrated an interface state density close to the conduction band edge below 2 X10 11 cm -2 eV -1, which is one or two orders-of-magnitude lower than that of MOS capacitors with oxides grown in dry O 2. The channel mobility of the n-channel 4H-SiC(0001) MISFETs with N-containing insulators is increased to about 30 cm 2/Vs. In addition, an even higher channel mobility of 50 cm 2/Vs has been realized by utilizing N-containing insulators adequately processed on the 4H-SiC(0001) face. From the experimental results, the dominant scattering mechanisms in SiC MISFETs have been identified; Coulomb scattering and electron trapping at interface states dominate the channel mobility in SiC MOSFETs with thermally-grown and deposited SiO 2. The application of N- containing insulators to p-channel 4H-SiC MIS devices is also discussed. © 2009 WILEY-VCH Verlag GmbH & Co.

    DOI: 10.1002/pssa.200925247

    Scopus

  186. A New Class of Step-and-Terrace Structure Observed on 4H-SiC(0001) after High-Temperature Gas Etching

    Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 2 ( 10 )   2009.10

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    Various interesting phenomena related to the step-and-terrace structures of crystal surfaces have been previously observed. In this paper, we report a unique phenomenon not observed previously: the formation of a new class of step-and-terrace structure on the 4H-SiC(0001) surface after high-temperature gas etching. The structure consists of a periodic array of pairs of 1-bilayer-height "down" steps and 5-bilayer-height "up" steps, in contrast to conventional step-and-terrace structures which consist of only "up" (or only "down") steps. We show that the newly observed (5 -1)-bilayer-height step-and-terrace structure originates from spiral etching at a screw dislocation. A mechanism for step-flow etching which conserves the "up"-and-"down" step pairs is also proposed. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.2.101603

    Web of Science

    Scopus

  187. Anomalously Large Difference in Ga Incorporation for AlGaN Grown on the (11(2)over-bar0) and (1(1)over-bar00) Planes under Group-III-Rich Conditions

    Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 2 ( 9 )   2009.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    The Ga incorporation behavior of AlGaN layers grown on nonpolar planes has been investigated comparing the (112̄0) and (11̄00) planes. AlGaN growth was performed on 4H-SiC(112̄0) and (11̄00) substrates by molecular-beam epitaxy under group-III-rich conditions. The Ga composition of the AlGaN layers was evaluated by energy-dispersive X-ray spectroscopy analysis as well as X-ray diffraction and cathodoluminescence measurements. The GaN mole fraction x of Al1-xGaxN layers grown on the (11̄00) plane is 0.12 for the Ga flux ratio [JGa/(JAl + J Ga)] of 0.32 at 750 °C, while it is negligibly small (x < 0.01) for growth on the (112̄0) plane. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/APEX.2.091003

    Web of Science

    Scopus

  188. P-Channel MOSFETs on 4H-SiC {0001} and Nonbasal Faces Fabricated by Oxide Deposition and N2O Annealing

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 56 ( 9 ) page: 1953 - 1958   2009.9

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Transactions on Electron Devices  

    In this paper, we have investigated 4H-SiC p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with deposited SiO2 followed by N2O annealing. In addition to deposited oxides, dry-O2-grown oxides and N2O-grown oxides were also adopted as the gate oxides of SiC p-channel MOSFETs. The MOSFETs have been fabricated on the 4H-SiC (0001), (0001), (0338), and (1120) faces. The (0001) MOSFETs with deposited oxides exhibited a relatively high channel mobility of 10 cm2, although a mobility of 7 cm2/V · swas obtained in the (0001) MOSFETs with N2O-grown oxides. The channel mobility was also increased by utilizing the deposited SiO2 in the MOSFETs fabricated on nonbasal faces, although the MOSFETs on (0001) were not operational. Compared with the thermally grown oxides, the deposited oxides annealed in N2O are effective in improving the performance of 4H-SiC p-channel MOSFETs. © 2009 IEEE.

    DOI: 10.1109/TED.2009.2025909

    Web of Science

    Scopus

  189. Mobility oscillation by one-dimensional quantum confinement in Si-nanowire metal-oxide-semiconductor field effect transistors

    Yoshioka Hironori, Morioka Naoya, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 106 ( 3 )   2009.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    Si-nanowire p -channel metal-oxide-semiconductor field effect transistors (MOSFETs), in which the typical cross section of the nanowire is a rectangular shape with 3 nm height and 18 nm width, have been fabricated and the current-voltage characteristics have been measured from 101 to 396 K. The transconductance has shown oscillation up to 309 K. The carrier transport has been theoretically analyzed, assuming that the acoustic phonon scattering is dominant. The electronic states have been determined from the effective mass approximation and the mobility from the relaxation time approximation as a function of the Fermi level. Relation between the gate voltage and the Fermi level has been estimated from the MOSFET structure. The calculated mobility has shown the oscillation with change in the Fermi level (the gate voltage), resulting in the transconductance oscillation. The oscillation originates from one-dimensional density of states (∝ E-0.5). © 2009 American Institute of Physics.

    DOI: 10.1063/1.3187803

    Web of Science

    Scopus

  190. 1580-V-40-m Omega . cm(2) Double-RESURF MOSFETs on 4H-SiC (000(1)over-bar)

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    IEEE ELECTRON DEVICE LETTERS   Vol. 30 ( 8 ) page: 831 - 833   2009.8

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IEEE Electron Device Letters  

    Double-reduced-surface-field (RESURF) MOSFETs with N2O-grown oxides have been fabricated on the 4H-SiC (0001 face. The double-RESURF structure is effective in reducing the drift resistance, as well as in increasing the breakdown voltage. In addition, by utilizing the 4H-SiC (0001̄) face, the channel mobility can be increased to over 30 cm2/V· s, and hence, the channel resistance is decreased. As a result, the fabricated MOSFETs on 4H-SiC (0001) have demonstrated a high breakdown voltage (VB) of 1580 V and a low on-resistance (RON of 40 mΩ · cm2. The figure-of-merit (VB2 of the fabricated device has reached 62 MW/cm2, which is the highest value among any lateral MOSFETs and is more than ten times higher than the "Si limit.". © 2009 IEEE.

    DOI: 10.1109/LED.2009.2023540

    Web of Science

    Scopus

  191. Temperature and doping dependencies of electrical properties in Al-doped 4H-SiC epitaxial layers

    Koizumi Atsushi, Suda Jun, Kimoto Tsunenobu

    JOURNAL OF APPLIED PHYSICS   Vol. 106 ( 1 )   2009.7

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The free hole concentration and the low-field transport properties of Al-doped 4H-SiC epilayers with several acceptor concentrations grown on semi-insulating substrates have been investigated in the temperature range from 100 to 500 K by Hall-effect measurements. Samples have been grown by cold-wall chemical vapor deposition (CVD) in the Al acceptor concentration range from 3× 1015 to 5.5× 1019 cm-3. The dependencies of the acceptor ionization ratio at 300 K and the ionization energy on the acceptor concentration were estimated. Numerical calculations of the hole Hall mobility and the Hall scattering factor have been performed based on the low-field transport model using relaxation-time approximation. At the low acceptor concentrations, the acoustic phonon scattering dominates the hole mobility at 300 K. At the high acceptor concentrations, on the other hand, the neutral impurity scattering dominates the mobility. A Caughey-Thomas mobility model with temperature dependent parameters is used to describe the dependence of the hole mobilities on the acceptor concentration, and the physical meanings of the parameters are discussed. © 2009 American Institute of Physics.

    DOI: 10.1063/1.3158565

    Web of Science

    Scopus

  192. Observation of novel defect structure in 2H-AlN grown on 6H-SiC(0001) substrates with 3-bilayer-height step-and-terrace structures

    Okumura Hironori, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 206 ( 6 ) page: 1187 - 1189   2009.6

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (A) Applications and Materials Science  

    250 nm thick AlN layers without a nucleation layer were grown directly on 6H-SiC(0001) with 3-bilayer-height steps by rf-plasma-assisted molecular-beam epitaxy. The structure and morphology of the AlN layers have been studied using atomic force microscopy, X-ray diffraction and transmission electron microscopy. Two different types of unique defect structures were observed. Rows of pure-edge-type threading dislocations were observed along the pre-existing step-edges of the SiC substrate for AlN grown on as-gas-etched SiC substrates, while the planar defects threading through the AlN layer were observed at the step-edges of the substrate for AlN on SiC with sacrificial oxidation. We concluded that these planar defects were the stacking mismatch boundaries due to the difference in stacking sequence of AlN layers on different SiC terraces. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssa.200880934

    Web of Science

    Scopus

  193. Triple Shockley type stacking faults in 4H-SiC epilayers

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS LETTERS   Vol. 94 ( 9 )   2009.3

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    4H-SiC epilayers have been characterized by microphotoluminescence (micro-PL) spectroscopy and micro-PL intensity mapping at room temperature. A type of stacking fault (SF) with a peak emission wavelength at 480 nm (2.58 eV) has been identified. The shape of this SF is triangular revealed by the micro-PL intensity mapping. Conventional and high-resolution transmission electron microscopies have been carried out to investigate the structure of this SF. Its stacking sequence is determined as (3,5) in Zhdanov's notation, which is consistent with that of the triple Shockley SF. The formation mechanism of this SF is also discussed. © 2009 American Institute of Physics.

    DOI: 10.1063/1.3095508

    Web of Science

    Scopus

  194. Systematic Investigation of c-Axis Tilt in GaN and AlGaN Grown on Vicinal SiC(0001) Substrates

    Suda Jun, Miyake Hiroki, Amari Koichi, Nakano Yuki, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 48 ( 2 )   2009.2

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    High-resolution X-ray diffraction measurements of GaN and AlGaN grown on 4H- and 6H-SiC(0001) vicinal substrates with rnisorientation angles of up to 9° are presented. Growth of (Al)GaN was carried out by plasma-assisted molecular beam epitaxy. The c-axis tilt, i.e., inclination of the (Al)GaN c-axis relative to that of SiC, was systematically investigated. The inclination angle clearly depended on the SiC substrate misorientation angle, while it was independent of the (Al)GaN growth temperature, SiC polytype, and substrate rnisorientation direction. The behavior observed for both GaN and AlGaN is in excellent agreement with the model proposed previously by Nagai for the InGaAs/GaAs system. © 2009 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.48.020202

    Web of Science

    Scopus

  195. 5 kV lateral double RESURF MOSFETs on 4H-SiC (000-1)C face

    Noborio M., Suda J., Kimoto T.

    Materials Science Forum   Vol. 615 617   page: 757 - 760   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    SiC lateral double RESURF MOSFETs have been fabricated on the 4H-SiC (000-1)C face. By utilizing the C face, the channel resistance can be reduced because the C-face MOSFETs show higher channel mobility than the Si-face MOSFETs. In addition, by employing the double RESURF structure, the drift resistance is decreased and the breakdown voltage is increased with increasing the RESURF doses. The fabricated RESURF MOSFETs on the 4H-SiC (000-1)C face have demonstrated a low on-resistance of 40 mΩcm2 at an oxide field of 3 MV/cm and a breakdown voltage of 1580 V at zero gate bias. The figure-of-merit of the MOSFET is 62 MW/cm2, which is more than 10 times better than the conventional "Si limit" and the highest value among any lateral MOSFETs to date. © (2009) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.615-617.757

    Scopus

  196. Bevel mesa combined with implanted junction termination structure for 10 kV SiC PiN diodes

    Hiyoshi T., Hori T., Suda J., Kimoto T.

    Materials Science Forum   Vol. 600-603   page: 995 - 998   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    A 10 kV 4H-SiC PiN diode with an improved junction termination structure has been fabricated. An improved bevel mesa structure, nearly vertical side-wall at the edge of pn junction and rounded corner at mesa bottom, has been formed by reactive ion etching (RIE). The junction termination extension (JTE) region has been optimized by device simulation, and simulated breakdown voltage has been compared with experimental results. The locations of electric field crowding and diode breakdown have been discussed. © (2009) Trans Tech Publications, Switzerland.

    DOI: 10.4028/3-908453-11-9.995

    Scopus

  197. Accurate measurements of second-order nonlinear-optical coefficients of silicon carbide

    Sato H., Shoji I., Suda J., Kondo T.

    Materials Science Forum   Vol. 615 617   page: 315 - 318   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    Second-order nonlinear-optical coefficients of 4H and 6H-SiC have been measured with the wedge technique. Using high-quality (11-20) samples as well as performing rigorous measurements and analyses, the three independent components, d31 (= d32), d15 (= d 24), and d33, have been accurately determined. We have found that the nonlinear-optical coefficients are nearly the same between the measured 4H and 6H-SiC samples within the experimental accuracy; d31 = 5.4 pm/V, d15 = 6.2 pm/V, and d33 = 9.7pm/V. © (2009) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.615-617.315

    Scopus

  198. Determination of the thermo-optic coefficients of GaN and AlN up to 515 degrees C

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, SUPPL 2   Vol. 6 ( SUPPL. 2 ) page: S776 - S779   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Physica Status Solidi (C) Current Topics in Solid State Physics  

    The refractive index dispersions of hexagonal GaN and AlN have been investigated to determine the thermo-optic coefficients. Measurements were conducted at temperatures ranging from room temperature up to 515 °C in the wavelength range from the near band-edge to 1000 nm. Optical interference measurements with vertical incident configuration were employed to precisely evaluate the ordinary refractive indices. Optical simulation of AlGaN/GaN distributed Bragg reflectors was also carried out by using the obtained thermo-optic coefficients. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI: 10.1002/pssc.200880937

    Web of Science

    Scopus

  199. High channel mobility in P-channel MOSFETs fabricated on 4H-SiC (0001) and non-basal faces

    Noborio M., Suda J., Kimoto T.

    Materials Science Forum   Vol. 615 617   page: 789 - 792   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    P-channel MOSFETs have been fabricated on 4H-SiC (0001) face as well as on 4H-SiC (03-38) and (11-20) faces. The gate oxides were formed by thermal oxidation in dry N2O ambient, which is widely accepted to improve the performance of n-channel SiC MOSFETs. The p-channel SiC MOSFETs with N 2O-grown oxides on 4H-SiC (0001), (03-38), and (11-20) faces show a channel mobility of 7 cm2/Vs, 11 cm2/Vs, and 17 cm 2/Vs, respectively. From the quasi-static C-V curves measured by using gate-controlled diodes, the interface state density was calculated by an original method. The interface state density was the lowest at the SiO 2/4H-SiC (03-38) interface (about 1×1012 cm -2eV-1 at EV + 0.2 eV). The authors have applied deposited oxides to the 4H-SiC p-channel MOSFETs. The (0001), (03-38), and (11-20) MOSFETs with deposited oxides exhibit a channel mobility of 10 cm 2/Vs, 13 cm2/Vs, and 17 cm2/Vs, respectively. The deposited oxides are one of effective approaches to improve both n-channel and p-channel 4H-SiC MOS devices. © (2009) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.615-617.789

    Scopus

  200. Enhanced channel mobility in 4H-SiC MISFETs by utilizing deposited SiN/SiO<inf>2</inf> stack gate structures

    Noborio M., Suda J., Kimoto T.

    Materials Science Forum   Vol. 600-603   page: 679 - 682   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    Deposited SiN/SiO2 stack gate structures have been investigated to improve the 4H-SiC MOS interface quality. Capacitance-voltage measurements on fabricated SiN/SiO2 stack gate MIS capacitors have indicated that the interface state density is reduced by post-deposition annealing in N 2O at 1300°C. The usage of thin SiN and increase in N 2O-annealing time lead to a low interface state density of 1×1011 cm-2eV-1 at EC - 0.2 eV. Oxidation of the SiN during N2O annealing has resulted in improvement of SiC MIS interface. The fabricated SiN/SiO2 stack gate MISFETs demonstrate a high channel mobility of 32 cm2/Vs on (0001)Si face and 40 cm2/Vs on (000-1)C face. © (2009) Trans Tech Publications, Switzerland.

    DOI: 10.4028/3-908453-11-9.679

    Scopus

  201. Improved current gain in GaN/SiC Heterojunction Bipolar Transistors by insertion of ultra-thin AlN layer at emitter-junction

    Miyake H., Kimoto T., Suda J.

    Materials Science Forum   Vol. 615 617   page: 979 - 982   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    GaN/SiC Heterojunction Bipolar Transistors (HBTs) with ultra-thin AlN insertion layers at the n-GaN/p-SiC emitter junction are proposed to improve carrier injection efficiency. The current-voltage characteristics of n-GaN/AlN/p-SiC heterojunctions have exhibited very small reverse leakage and good rectification. The capacitance-voltage measurement have revealed that the conduction band offset between n-GaN and p-SiC has been reduced from -0.74 eV to -0.54 eV by insertion of AlN, indicating that the GaN/AlN/SiC heterojunction may show better electron-injection efficiency. A significantly improved common-base current gain (α∼0.2) is obtained for GaN/AlN/SiC HBTs with initial N* pre-irradiation, while it was very low (α∼0.001) for GaN/SiC HBTs without AlN layers. © (2009) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.615-617.979

    Scopus

  202. Improved on-current of 4H-SiC MOSFETs with a three-dimensional gate structure

    Nanen Y., Yoshioka H., Noborio M., Suda J., Kimoto T.

    Materials Science Forum   Vol. 615 617   page: 753 - 756   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    4H-SiC (0001) MOSFETs with a three-dimensional gate structure, which has a top channel on the (0001) face and side-wall channels on the {11-20} face have been fabricated. The three-dimensional gate structures with a 1-5 μm width and 0.8 μm height have been formed by reactive ion etching, and the gate oxide has been deposited by plasma-enhanced chemical vapor deposition and then annealed in N2O ambient at 1300°C. The fabricated MOSFETs have exhibited superior characteristics: ION / IOFF, the subthreshold swing and VTH are 1010, 250 mV/decade and 3.5 V, respectively. The drain current normalized by the gate width is increasing with decreasing the gate width. The normalized drain current of a 1 μm-wide MOSFET is ten times higher than that of a conventional planar MOSFET. © (2009) Trans Tech Publications.

    DOI: 10.4028/www.scientific.net/MSF.615-617.753

    Scopus

  203. Spatial profiling of planar defects in 4H-SiC epilayers using micro-photoluminescence mapping

    Feng G., Suda J., Kimoto T.

    Materials Science Forum   Vol. 615 617   page: 245 - 250   2009

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Materials Science Forum  

    The micro-photoluminescence (micro-PL) spectroscopy and its intensity mapping have been utilized to investigate the planar defects, stacking faults (SFs), in 4H-SiC epilayers. Strong PL emissions from the SFs are observed even at room temperature. It is found that each kind of SF shows the distinct PL emission behaviours. Three kinds of SFs: intrinsic Frank SFs, double Shockley SFs, and in-grown SFs, have been identified in the samples based on the micro-PL spectra. At the same time, the micro-PL intensity mapping at the emission band of each SF has been performed to spatially profile the SFs. The shapes, distributions, and densities of SFs in the epilayers are then presented. The PL emission behaviours of each SF at low temperature are also studied. © (2009) Trans Tech Publications, Switzerland.

    DOI: 10.4028/www.scientific.net/MSF.615-617.245

    Scopus

  204. The temperature dependence of the refractive indices of GaN and AlN from room temperature up to 515 degrees C

    Watanabe Naoki, Kimoto Tsunenobu, Suda Jun

    JOURNAL OF APPLIED PHYSICS   Vol. 104 ( 10 )   2008.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Applied Physics  

    The temperature dependence of the refractive indices of GaN and AlN was investigated in the wavelength range from the near band edge (367 nm for GaN and 217 nm for AlN) to 1000 nm and the temperature range from room temperature to 515 °C. Optical interference measurements with vertical incident configuration were employed to precisely evaluate the ordinary refractive indices. © 2008 American Institute of Physics.

    DOI: 10.1063/1.3021148

    Web of Science

    Scopus

  205. N2O-grown oxides/4H-SiC (0001), (0338), and (1120) interface properties characterized by using p-type gate-controlled diodes

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS LETTERS   Vol. 93 ( 19 )   2008.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    The N2 O -grown SiO2 /4H-SiC (0001), (033̄8), and (112̄0) interface properties in p -channel metal-oxide-semiconductor field-effect transistors (MOSFETs) have been characterized by using gate-controlled diodes. Although the inversion layer is not formed in simple SiC MOS capacitors at room temperature due to its large bandgap, a standard low frequency capacitance-voltage (C-V) curve can be obtained for the gate-controlled diodes, owing to the supply of minority carriers from the source region. From the quasistatic C-V curves measured by using gate-controlled diodes, the interface state density has been evaluated by an original method proposed in this study. The interface state density near the valence band edge evaluated by the method is the lowest at the oxides/ 4H-SiC (033̄8) interface. Comparison with the channel mobility is also discussed. © 2008 American Institute of Physics.

    DOI: 10.1063/1.3028016

    Web of Science

    Scopus

  206. Surface Morphologies of 4H-SiC(11(2)over-bar0) and (1(1)over-bar00) Treated by High-Temperature Gas Etching

    Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 47 ( 11 ) page: 8388 - 8390   2008.11

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japanese Journal of Applied Physics  

    The impact of HCl/H2 high-temperature gas-etching on the surface morphologies of 4H-SiC(1120) and (1100) faces is investigated by atomic force microscopy (AFM). Very flat surfaces are obtained on both (1120) and (11̄00) faces after gas-etching when the substrate surfaces are initially treated by chemical mechanical polishing to remove polishing scratches. The root-mean square roughness values of gas-etched (112̄0) and (11̄00) substrates are 0.07 and 0.11nm, respectively. Within AFM resolution limits no atomic steps are observed on the very flat surfaces of (1120) substrates. On the other hand, clear step-and-terrace structures are observed on (1100) substrates after gas-etching and the height of the steps (2.7Å) corresponding to the lattice spacing between 4H-SiC(1100) planes (= √3a/2). © 2008 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.47.8388

    Web of Science

    Scopus

  207. Improved Performance of 4H-SiC Double Reduced Surface Field Metal-Oxide-Semiconductor Field-Effect Transistors by Increasing RESURF Doses

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS EXPRESS   Vol. 1 ( 10 )   2008.10

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1143/APEX.1.101403

    Web of Science

  208. Improvement of Channel Mobility in Inversion-Type n-Channel GaN Metal-Oxide-Semiconductor Field-Effect Transistor by High-Temperature Annealing

    Yamaji Kazuki, Noborio Masato, Suda Jun, Kimoto Tsunenobu

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 47 ( 10 ) page: 7784 - 7787   2008.10

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1143/JJAP.47.7784

    Web of Science

  209. Impact of surface step heights of 6H-SiC (0001) vicinal substrates in heteroepitaxial growth of 2H-AlN

    Okumura H., Horita M., Kimoto T., Suda J.

    APPLIED SURFACE SCIENCE   Vol. 254 ( 23 ) page: 7858 - 7860   2008.9

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.apsusc.2008.02.165

    Web of Science

  210. Nonpolar 4H-AlN grown on 4H-SiC (1(1)over-bar00) with reduced stacking fault density realized by persistent layer-by-layer growth

    Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 93 ( 8 )   2008.8

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.2976559

    Web of Science

  211. 4H-SiC MIS capacitors and MISFETs with deposited SiNx/SiO2 stack-gate structures

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 55 ( 8 ) page: 2054 - 2060   2008.8

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/TED.2008.926644

    Web of Science

  212. Hydrogen implantation and annealing-induced exfoliation process in SiC wafers with various crystal orientations

    Senga Kei, Kimoto Tsunenobu, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 47 ( 7 ) page: 5352 - 5354   2008.7

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1143/JJAP.47.5352

    Web of Science

  213. Lifetime-killing defects in 4H-SiC epilayers and lifetime control by low-energy electron irradiation

    Kimoto Tsunenobu, Danno Katsunori, Suda Jun

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   Vol. 245 ( 7 ) page: 1327 - 1336   2008.7

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/pssb.200844076

    Web of Science

  214. Characterization of stacking faults in 4H-SiC epilayers by room-temperature microphotoluminescence mapping

    Feng Gan, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS LETTERS   Vol. 92 ( 22 )   2008.6

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.2937097

    Web of Science

  215. 4H-SiC double RESURF MOSFETs with a record performance by increasing RESURF dose

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    ISPSD 08: PROCEEDINGS OF THE 20TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS     page: 263 - 266   2008

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  216. Temperature dependence of electrical properties of NiO thin films for Resistive Random Access Memory

    Suzuki Ryota, Suda Jun, Kimoto Tsunenobu

    MATERIALS SCIENCE AND TECHNOLOGY FOR NONVOLATILE MEMORIES   Vol. 1071   page: 69 - 74   2008

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  217. 4H-SiC lateral double RESURF MOSFETs with low ON resistance

    Noborio Masato, Suda Jun, Kimoto Tsunenobu

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 54 ( 5 ) page: 1216 - 1223   2007.5

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/TED.2007.894249

    Web of Science

  218. High-quality nonpolar 4H-AlN grown on 4H-SiC (11(2)over-bar20) substrate by molecular-beam epitaxy

    Horita Masahiro, Suda Jun, Kimoto Tsunenobu

    APPLIED PHYSICS LETTERS   Vol. 89 ( 11 )   2006.9

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.2352713

    Web of Science

  219. Characterization of ZrB2(0001) surface prepared by ex situ HF solution treatment toward applications as a substrate for GaN growth

    Armitage R, Suda J, Kimoto T

    SURFACE SCIENCE   Vol. 600 ( 7 ) page: 1439 - 1449   2006.4

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.susc.2006.01.032

    Web of Science

  220. Epitaxy of nonpolar AlN on 4H-SiC (1-100) substrates

    Armitage R, Suda J, Kimoto T

    APPLIED PHYSICS LETTERS   Vol. 88 ( 1 )   2006.1

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.2161809

    Web of Science

  221. Anisotropic etching of single crystalline SiC using molten KOH for SiC bulk micromachining

    Fukunaga Katsuhiko, Suda Jun, Kimoto Tsunenobu

    MICROMACHINING AND MICROFABRICATION PROCESS TECHNOLOGY XI   Vol. 6109   2006

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1117/12.647116

    Web of Science

  222. 1330 V, 67 m Omega center dot cm(2) 4H-SiC(0001) RESURF MOSFET

    Kimoto T, Kawano H, Suda J

    IEEE ELECTRON DEVICE LETTERS   Vol. 26 ( 9 ) page: 649 - 651   2005.9

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/LED.2005.854371

    Web of Science

  223. Experimental and theoretical investigations on short-channel effects in 4H-SiC MOSFETs

    Noborio M, Kanzaki Y, Suda J, Kimoto T

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 52 ( 9 ) page: 1954 - 1962   2005.9

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/TED.2005.854269

    Web of Science

  224. Design and Fabrication of RESURF MOSFETs on 4H-SiC(0001), (1120), and 6H-SiC(0001)

    Kimoto T, Kosugi H, Suda J, Kanzaki Y, Matsunami H

    IEEE TRANSACTIONS ON ELECTRON DEVICES   Vol. 52 ( 1 ) page: 112 - 117   2005.1

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/TED.2004.841358

    Web of Science

  225. 1200 V-class 4H-SiC RIESURF MOSFETs with low on-resistances

    Kimoto T, Kawano H, Suda J

    PROCEEDINGS OF THE 17TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS     page: 279 - 282   2005

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  226. Molecular beam epitaxy of GaN on lattice-matched ZrB2 substrates using low-temperature GaN and AlN nucleation layers

    Armitage R, Nishizono K, Suda J, Kimoto T

    GaN, AIN, InN and Their Alloys   Vol. 831   page: 477 - 482   2005

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  227. Short-Channel Effects in 4H-SiC MOSFETs

    Noborio M, Kanzaki Y, Suda J, Kimoto T, Matsunami H

    SILICON CARBIDE AND RELATED MATERIALS 2004   Vol. 483   page: 821 - 824   2005

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  228. Molecular-beam epitaxy of III-N on novel ZrB2 substrates

    Suda J

    PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XII   Vol. 5349   page: 397 - 407   2004

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  229. Fabrication of SiC lateral super junction diodes with multiple stacking p- and n-layers

    Miura M, Nakamura S, Suda J, Kimoto T, Matsunami H

    IEEE ELECTRON DEVICE LETTERS   Vol. 24 ( 5 ) page: 321 - 323   2003.5

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1109/LED.2003.812561

    Web of Science

  230. Epitaxial growth of AlN on 6H-SiC (11(2)over-bar0) by molecular-beam epitaxy and effect of low-temperature buffer layer

    Onojima N, Suda J, Matsunami H

    GAN AND RELATED ALLOYS-2002   Vol. 743   page: 139 - 144   2003

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  231. Growth of high-quality non-polar AlN on 4H-SiC(11-20) substrate by molecular-beam epitaxy

    Onojima N, Suda J, Kimoto T, Matsunami H

    5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS   Vol. 0 ( 7 ) page: 2502 - 2505   2003

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/pssc.200303396

    Web of Science

  232. Impact of SiC surface control on initial growth mode and crystalline quality of AlN grown by molecular-beam epitaxy

    Onojima N, Suda J, Kimoto T, Matsunami H

    5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS   Vol. 0 ( 7 ) page: 2529 - 2532   2003

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/pssc.200303358

    Web of Science

  233. Lattice relaxation of AlN buffer on surface-treated SiC in molecular-beam epitaxy for growth of high-quality GaN

    Suda J, Miura K, Honaga M, Onojima N, Nishi Y, Matsunami H

    GAN AND RELATED ALLOYS-2002   Vol. 743   page: 311 - 316   2003

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  234. Surface control of ZrB2 (0001) substrate for molecular-beam epitaxy of GaN

    Suda J, Yamashita H, Armitage R, Kimoto T, Matsunami H

    GAN AND RELATED ALLOYS - 2003   Vol. 798   page: 369 - 374   2003

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  235. Effects of 6H-SiC surface reconstruction on lattice relaxation of AlN buffer layers in molecular-beam epitaxial growth of GaN

    Suda J, Miura K, Honaga M, Nishi Y, Onojima N, Matsunami H

    APPLIED PHYSICS LETTERS   Vol. 81 ( 27 ) page: 5141 - 5143   2002.12

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1063/1.1533855

    Web of Science

  236. Growth of AlN (11(2)over-bar0) on 6H-SiC (11(2)over-bar0) by molecular-beam epitaxy

    Onojima N, Suda J, Matsunami H

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 41 ( 12A ) page: L1348 - L1350   2002.12

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1143/JJAP.41.L1348

    Web of Science

  237. Heteroepitaxial growth of group-III nitrides on lattice-matched metal boride ZrB2 (0001) by molecular beam epitaxy

    Suda J, Matsunami H

    JOURNAL OF CRYSTAL GROWTH   Vol. 237   page: 1114 - 1117   2002.4

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  238. Lattice relaxation process of AlN growth on atomically flat 6H-SiC substrate in molecular beam epitaxy

    Onojima N, Suda J, Matsunami H

    JOURNAL OF CRYSTAL GROWTH   Vol. 237   page: 1012 - 1016   2002.4

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  239. Scanning capacitance and spreading resistance microscopy of SiC multiple-pn-junction structure

    Suda J, Nakamura S, Miura M, Kimoto T, Matsunami H

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 41 ( 1AB ) page: L40 - L42   2002.1

     More details

    Publishing type:Research paper (scientific journal)  

    DOI: 10.1143/JJAP.41.L40

    Web of Science

  240. Molecular-beam epitaxial growth of insulating AlN on surface-controlled 6H-SiC substrate by HCl gas etching

    Onojima N, Suda J, Matsunami H

    APPLIED PHYSICS LETTERS   Vol. 80 ( 1 ) page: 76 - 78   2002.1

     More details

    Language:Japanese   Publishing type:Research paper (scientific journal)  

    Web of Science

  241. Scanning capacitance microscopy of SiC multiple PN junction structure grown by cold-wall chemical vapor deposition

    Suda J, Nakamura S, Miura M, Kimoto T, Matsunami H

    SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS   Vol. 389-3   page: 659 - 662   2002

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  242. Selective area growth of cubic GaN on 3C-SiC (001) by metalorganic molecular beam epitaxy

    Suda J, Kurobe T, Nakamura S, Matsunami H

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 39 ( 11A ) page: L1081 - L1083   2000.11

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  243. GaP/Si heterojunction with ohmic conduction fabricated by wafer fusion technique

    Soeno A, Kajita D, Suda J, Matsunami H

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 39 ( 9AB ) page: L905 - L907   2000.9

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  244. Preferential growth mode of cubic GaN by metalorganic molecular beam epitaxy on sapphire (0001) substrates

    Suda J, Kurobe T, Masuda T, Matsunami H

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE   Vol. 176 ( 1 ) page: 503 - 507   1999.11

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  245. Growth evolution of cubic-GaN on sapphire (0001) substrate by metalorganic molecular beam epitaxy

    Suda J, Kurobe T, Matsunami H

    JOURNAL OF CRYSTAL GROWTH   Vol. 201   page: 437 - 440   1999.5

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  246. Preferential growth of cubic GaN on sapphire (0001) substrates by metal organic molecular beam epitaxy

    Kurobe T, Sekiguchi Y, Suda J, Yoshimoto M, Matsunami H

    APPLIED PHYSICS LETTERS   Vol. 73 ( 16 ) page: 2305 - 2307   1998.10

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  247. Optical properties of light-hole excitons in ZnSSe/ZnMgSSe tensile-strained quantum wells

    Suda J, Ogawa M, Sakurai K, Kawakami Y, Fujita S, Fujita S

    JOURNAL OF CRYSTAL GROWTH   Vol. 184   page: 863 - 866   1998.2

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  248. Hydrogen sulfide treatment of GaAs substrate and its effects on initial stage of ZnSe growth

    Suda J, Tokutome R, Kawakami Y, Fujita S, Fujita S

    JOURNAL OF CRYSTAL GROWTH   Vol. 175   page: 593 - 597   1997.5

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  249. Surface reconstruction and morphology of hydrogen sulfide treated GaAs (001) substrate

    Suda J, Kawakami Y, Fujita S, Fujita S

    CONTROL OF SEMICONDUCTOR SURFACES AND INTERFACES   Vol. 448   page: 15 - 20   1997

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  250. (2x6) surface reconstruction of GaAs (001) obtained by hydrogen sulfide irradiation

    Suda J, Kawakami Y, Fujita S, Fujita S

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   Vol. 35 ( 11B ) page: L1498 - L1500   1996.11

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  251. Growth of p-type ZnSe by metalorganic molecular beam epitaxy using metal Zn and dimethylselenide

    Suda J, Tsuka M, Honda D, Funato M, Kawakami Y, Fujita S, Fujita S

    JOURNAL OF ELECTRONIC MATERIALS   Vol. 25 ( 2 ) page: 223 - 227   1996.2

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  252. The role of defects on radiative transitions in nitrogen doped ZnSe

    Hauksson IS, Suda J, Tsuka M, Kawakami Y, Fujita S, Fujita S

    JOURNAL OF CRYSTAL GROWTH   Vol. 159 ( 1-4 ) page: 329 - 333   1996.2

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  253. GROWTH OF ZNSE/ZNMGSSE QUANTUM-WELL STRUCTURES BY METALORGANIC MOLECULAR-BEAM EPITAXY UNDER IN-SITU OBSERVATION OF REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION INTENSITY OSCILLATION

    SUDA J, KAWAKAMI Y, FUJITA S, FUJITA S

    JOURNAL OF CRYSTAL GROWTH   Vol. 150 ( 1-4 ) page: 738 - 742   1995.5

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  254. OPTICAL-PROPERTIES OF ZNSE/ZNMGSSE SINGLE QUANTUM-WELLS GROWN BY METALORGANIC MOLECULAR-BEAM EPITAXY

    SUDA J, KAWAKAMI Y, FUJITA S, FUJITA S

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 33 ( 7B ) page: L986 - L989   1994.7

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  255. GAS-SOURCE MOLECULAR-BEAM EPITAXIAL-GROWTH OF (ZN,MG)(S,SE) USING BIS-METHYLCYCLOPENTADIENYL-MAGNESIUM AND HYDROGEN-SULFIDE

    SUDA J, KAWAKAMI Y, FUJITA S, FUJITA S

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS   Vol. 33 ( 3A ) page: L290 - L293   1994.3

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

  256. GAS-SOURCE MBE OF ZNMGSSE LAYERS

    FUJITA S, SUDA J, KAWAKAMI Y, FUJITA S

    II-VI BLUE/GREEN LASER DIODES   Vol. 2346   page: 40 - 47   1994

     More details

    Publishing type:Research paper (scientific journal)  

    Web of Science

▼display all

Books 2

  1. Lifetime-Killing Defects in 4H-SiC Epilayers and Lifetime Control by Low-Energy Electron Irradiation

    Kimoto T., Danno K., Suda J.( Role: Sole author)

    Silicon Carbide  2011.4  ( ISBN:9783527409532

     More details

    Language:Japanese

    DOI: 10.1002/9783527629053.ch10

    Scopus

  2. 4H-SiC MISFETs with Nitrogen-Containing Insulators

    Noborio M., Suda J., Beljakowa S., Krieger M., Kimoto T.( Role: Sole author)

    Silicon Carbide  2011.3  ( ISBN:9783527409976

     More details

    Language:Japanese

    DOI: 10.1002/9783527629077.ch10

    Scopus

KAKENHI (Grants-in-Aid for Scientific Research) 20

  1. 炭化珪素基板上へのⅢ族窒化物の超高品質コヒーレント成長の基礎とデバイス応用

    2012.4 - 2016.3

    科学研究費補助金  基盤研究(B)

    須田 淳

      More details

    Authorship:Principal investigator 

    SiC基板上への高Al組成窒化物半導体のコヒーレント成長の基礎を築き、デバイス応用への展開を目指して研究を行った。高Al組成AlGaNの成長として、組成や構造のデジタル的な制御が可能な、AlN/GaN短周期超格子に着目した。さまざまな構造・成長条件のAlN/GaN短周期超格子の臨界膜厚の解明、緩和メカニズムの解明を行い、GaNモル分率20%の規則混晶のコヒーレント成長に成功した。また、3BLのGaNを成長すると格子緩和がはじまることを明らかにした。極薄GaNの格子緩和はゆっくりと生じることを利用して、SiC基板上に圧縮、引っ張り歪みを持つAlNを成長する方法も提案した。

  2. 炭化珪素半導体の欠陥制御と超高耐圧ロバスト素子への応用

    2009.4 - 2014.3

    科学研究費補助金  基盤研究(S)

    木本 恒暢

      More details

    電力系統や高圧電源に用いられる高効率電力変換用パワーデバイスの実現を目指し、炭化珪素(SiC)半導体に関する材料科学と超高耐圧デバイスの基礎研究を遂行した。主な成果として、高純度結晶の作製、拡張欠陥の構造および物性の解明、拡張欠陥の非破壊高速検出、深い準位の物性解明、キャリア寿命キラー欠陥の大幅な低減とキャリア寿命の増大、キャリア寿命制御、超高耐圧を可能とする接合終端構造および設計指針の提示、絶縁破壊機構に関する考察、固体素子として最高の超高耐圧(20kV以上) SiC PiNダイオードおよびバイポーラトランジスタの作製、特性解析と高温動作(300℃)の実証を達成した。

  3. 超高耐圧ロバスト素子を目指した炭化珪素半導体の欠陥制御に関する研究

    2009.4 - 2010.3

    科学研究費補助金  基盤研究(A)

    木本 恒暢

      More details

    Authorship:Coinvestigator(s) 

  4. 新しい結晶構造を持つ窒化アルミニウムの物性制御と深紫外発光デバイスへの展開

    2008.4 - 2011.3

    科学研究費補助金  基盤研究(B)

      More details

    Authorship:Principal investigator 

  5. イオン注入および埋め込み再成長を利用したSiC超接合パワーMOSFETの研究

    2006.4 - 2009.3

    科学研究費補助金  基盤研究(A)

    木本 恒暢

      More details

    Authorship:Coinvestigator(s) 

  6. ヘテロバレント・ヘテロポリタイプSiC上III族窒化物結晶成長の総合的理解と制御

    2004.4 - 2007.3

    科学研究費補助金  若手研究(A)

      More details

    Authorship:Principal investigator 

  7. Dislocation passivation in InGaN by intentinally using immiscible nature during MBE growth by DERI method

    Grant number:26600090  2014.4 - 2017.3

    NANISHI YASUSHI

      More details

    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

    InGaN alloys are currently widely used as active layers of blue LEDs. Optical and electronic characteristics are degraded dramatically, however, when we increase In composition to fabricate green, red and infra-red LEDs due to generation of dislocations. In this study, we tried to suppress this dislocation effect by using DERI method, newly developed RF-MBE growth method by us, for high quality InN growth. Intentionally utilizing immiscible nature of InGaN alloys, we grew Ga-rich InGaN surrounding dislocations with wider bandgap. It was found that leakage current due to dislocation was suppressed as expected by conductive AFM measurements.

  8. Coherent growth of high-quality group-III nitirides on SiC substrates and its device applications

    Grant number:24360009  2012.4 - 2016.3

    Suda Jun

      More details

    Authorship:Principal investigator 

    Grant amount:\18590000 ( Direct Cost: \14300000 、 Indirect Cost:\4290000 )

    Coherent Growth of high-Al-content AlGaN on SiC substrates aiming at device applications were investigated. As high-Al-content AlGaN, AlN/GaN short-period superlattices were grown. Various kinds of AlN/GaN Superlattices were grown to assess critical composition as well as critical thickness for coherent growth on SiC substrates. Superlattices with GaN mole fraction of 20% were successfully growth coherently. On the other hand, it was found that growth of 3-bilayer-thick GaN results in lattice relaxation. The relaxation was gradual. By using this nature, strain-controlled AlN were grown on SiC substrates via ultra-thin GaN/AlN multilayer structures.

  9. Temperature independent SiC photodetector operating up to 500 degreeC

    Grant number:24656230  2012.4 - 2014.3

    SUDA Jun

      More details

    Authorship:Principal investigator 

    Grant amount:\4030000 ( Direct Cost: \3100000 、 Indirect Cost:\930000 )

    Ultra-violet photo detectors which can be operated up to 500 degreeC are needed for monitoring system of power plant and chemical plant. Such photo detectors are also expected to be used in engine combustion monitoring for automotive or aerospace field. Silicon (Si) which is mainly used in nowadays electronics cannot be operated at over 200 degreeC due to its small energy bandgap of 1.12 eV. Wide-bandgap semiconductor, silicon carbide (4H-SiC) is promising candidate for such photo detectors. In this study, we investigated optical properties of SiC, which are required for device design. We also found effective suppression method of leakage current which degrades sensitivity of photo detector. Based on these results, we successfully demonstrated operation of SiC photo detectors at 500 degree C.

  10. Defect Engineering in SiC and Application to Robust Devices with Ultrahigh Blocking Voltage

    Grant number:21226008  2009.5 - 2014.3

    KIMOTO Tsunenobu

      More details

    Authorship:Coinvestigator(s) 

    Defect electronics in SiC and ultrahigh-voltage SiC power devices have been studied toward efficient electric power conversion employed for future smart grids. Fast epitaxy of high-purity SiC was developed, and extended defects in SiC epitaxial layers were systematically characterized. Physical properties of the major deep levels were elucidated. The carrier-lifetime killer defects could be eliminated, leading to remarkably enhanced carrier lifetimes. Control of carrier lifetimes was also achieved. Original junction-termination structures were proposed to achieve ultrahigh blocking voltage with SiC, and breakdown mechanism of SiC devices was discussed. By utilizing thick, lightly-doped SiC epitaxial layers and the original device structures, ultrahigh-voltage (> 20 kV) PiN diodes and npn bipolar transistors were realized. The performance was significantly improved by enhancement of carrier lifetimes, and high-temperature operation of SiC devices was demonstrated.

  11. 超高耐圧ロバスト素子を目指した炭化珪素半導体の欠陥制御に関する研究

    Grant number:21246051  2009

    木本 恒暢

      More details

    Authorship:Coinvestigator(s) 

    超高耐圧素子の作製に必要な高純度・厚膜SiCエピタキシャル成長層の形成と欠陥評価について研究を行った。得られた成果は以下のとおりである。
    (1)独自の化学気相堆積法により、70-90μm/hの高速で70-160μmの厚膜SiCエピタキシャル成長層を形成することに成功した。成長層の表面は原子レベルで平坦であり、残留不純物密度が約1E13/cm3という高純度結晶を得た。また、SiCパワーデバイスの信頼性に悪影響を及ぼす基底面転位(基板から伝播)の密度が、成長速度の上昇と共に減少することを見出した。
    (2)フォトルミネッセンス(PL)のマッピング測定により、SiC成長層中に存在するin-grown積層欠陥を高速・非破壊に検出できることを示した。SiC成長層中に存在する主要なin-grown積層欠陥には3種類あり、高分解能断面電子顕微鏡(TEM)観察により、各々の欠陥構造を原子レベルで明らかにした。さらに、成長初期プロセスの改良により、積層欠陥密度を大幅に低減することに成功した。
    (3)n型SiC成長層に存在する点欠陥(深い準位)をショットキー障壁容量の過渡特性解析(DLTS)により評価した。伝導帯底から約0.6eVおよび1.5eVのエネルギー位置に主要な電子トラップが存在すること、およびこれらの点欠陥は1700℃の高温熱処理を施すことにより、密度を大幅に低減できることを明らかにした。

  12. Accurate measurements of the second-order nonlinear-optical coefficients of SiC

    Grant number:20560038  2008 - 2010

    SHOJI Ichiro

      More details

    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

    We have accurately measured the second-order nonlinear-optical coefficients of SiC, which is expected to be a material for next-generation high-power frequency-conversion devices. We carried out the measurements with several combinations of different manufacturers, polytypes, surface orientations of the samples, and different measurement techniques at the fundamental wavelength of 1.064 μm. The same accurate values were obtained for the same polytype samples, and d33 of 4H-SiC was found to be 6 % smaller than that of 6H-SiC. The magnitudes of the nonlinear-optical coefficients determined in this research should be useful for precise design of high-power and highly efficient frequency-conversion devices using SiC.

  13. Growth of aluminum nitride with a new crystal structure for deep-ultraviolet light emitting devices

    Grant number:20360008  2008 - 2010

    SUDA Jun

      More details

    Authorship:Principal investigator 

    Grant amount:\18590000 ( Direct Cost: \14300000 、 Indirect Cost:\4290000 )

    Aluminum nitride (AlN) has attracted much attention as a material for deep-ultraviolet light emitting devices. Thermally stable structure of AlN is known to be wurtzite structure. On the other hand, AlN studied in this project has 4H structure. 4H-AlN can be obtained by isopolytypic growth on 4H-SiC. Thanks to isopolytypic growth, 4H-AlN grown on 4H-SiC shows excellent crystalline quality. In this study, growth of AlGaN alloy and AlGaN/AlN quantum well structures were studied. 4H-AlGaN/AlN quantum well structures were successfully grown on 4H-SiC (1-100). We revealed that growth of high-quality 4H-AlGaN on 4H-SiC (11-20) is impossible. We proposed 4H-GaN/AlN short-period super lattice structures instead of 4H-AlGaN. The 4H-GaN/AlN short-period super lattice structures were successfully grown on 4H-SiC (11-20).

  14. 窒化物半導体の非線形光学定数の精密評価と内部電界による制御

    Grant number:19032003  2007 - 2008

    近藤 高志

      More details

    Authorship:Coinvestigator(s) 

    バルク試料を用いた回転型メーカーフリンジ法とウェッジ法とを併用することでSiCとGaNのintrmsicな非線形光学定数(d=x^<(2)>/2)の精密測定をおこなった。また, MBE法によるGaN周期極性反転構造の作製と導波路作製に取り組んだ。
    1. SiCの非線形光学定数精密測定
    GaNエピタキシャル薄膜の非線形光学定数をはかる準備として, 基板材料となるSiCの非線形光学定数評価をおこなった。その結果は以下のとおり。6H-SiCの非線形光学定数は, d_<31>=6.7pm/V, d_<15>=6.5pm/V, d_<33>=-12.5pm/V。4H-SiCの非線形光学定数は, d_<31>=6.5pm/V, d_<15>=6.7pm/V, d_<33>=-11.7pm/V。両者は測定誤差の範囲内で一致しているが, 4H-SiCのd_<33>が若干小さく, 理想的四面体構造に対して予想されるd_<33>/d_<31>=-2からのずれが大きい。これは, 4H-SICが6H-SiCと比較して格子の歪みが大きいことを反映している。
    2. GaNの非線形光学定数精密測定
    液相成長のバルク試料とエピタキシャル成長自立基板を試料として用い, GaNのintrinsicな非線形光学定数の精密測定をおこない, 以下の結果が得られた。d_<31>=2.4pm/V, d_<15>=2.5pm/V, d_<33>=-3.8pm/V。GaNは理想的四面体構造からの歪みが大きく, その結果, d_<33>/d_<31>=-2の関係から大きくずれている。また, この結果は, エピタキシャル薄膜試料を用いて測定された既報の値と比較してかなり小さく, これまでの測定に内部電界と3次非線形光学効果の影響が混入していたことをうかがわせる。
    3. 周期極性反転GaN導波路の作製
    MBEによるGaNエピタキシャル膜の格子極性制御の再現性を確認した上で, 疑似位相整合波長変換デバイス作製に不可欠な周期極性反転GaNの作製をおこなった。また, 導波路デバイス作製プロセス開発の第一段階としてリフトオフによるリブ構造作製が可能であることを示した。

  15. Study on SiC Super-Junction Power MOSFETs Utilizing Ion Implantation and Embedded Epitaxial Growth

    Grant number:18206032  2006 - 2008

    TSUNENOBU Kimoto

      More details

    Authorship:Coinvestigator(s) 

  16. ヘテロバレント・ヘテロポリタイプSiC上III族窒化物結晶成長の総合的理解と制御

    Grant number:16686002  2004 - 2006

    須田 淳

      More details

    Authorship:Principal investigator 

    Grant amount:\28600000 ( Direct Cost: \22000000 、 Indirect Cost:\6600000 )

    ヘテロバレソト・ヘテロポリタイプな系である、AlN/SiCヘテロエピタキシャル成長についての系統的な研究を行った。無極性面方位に関しては、(1-100)面、(11-20)面を対象に研究を行った。4H-SiCを用いた場合に、SiCの4層周期の積層構造がAlNに転写され、AlNは4H構造を持つことが明らかになった。SiC表面の原子レベルの平坦化とAlN成長条件の最適化を行うことで、きわめて欠陥の少ない4H-AlNを成長することに成功した。無極性面方位に関しては、成長条件を適切に設定することで、本来ヘテロポリタイプであるAlN/SiC系をアイソポリタイプ化し、結晶欠陥を大幅に低減できることが明らかになった。このアイソポリタイプAlNをテンプレートとして、デバイス応用上重要なGaNの成長を行った。広範囲な成長条件の検討を行ったが、GaNのポリタイプは熱力学的に安定な2H構造になってしまうことが判明した。AlN/GaNの格子不整合がAlN/SiCの倍以上であることや、GaNそれ自体が4H構造となった場合エネルギー的に不安定になることが原因として考えられるが、現時点では不明である。2H構造GaNは4H構造AlNほどは高品質ではないが、他の無極性基板と同等の品質のものが得られることは確認している。極性面については、SiCのステツプェツジに起因する欠陥の極限までの低減を目指して研究を進めた。ウエハーレベルでのSiCのステップエッジの高さ制御技術をほぼ確立し、6H-SiCにおいてステップ高さ6層に制御した基板を作製し、この表面上にAlNを成長し、結晶欠陥の低減を確認した。

  17. Fundamental Study on Low-loss SiC Power Devices Using Multi pn Junctions

    Grant number:16360153  2004 - 2005

    KIMOTO Tsunenobu

      More details

    Authorship:Coinvestigator(s) 

    In this research project, designing and fabrication of low-loss, high-voltage silicon carbide (SiC) power devices with multi pn junction structures have been investigated. In the multi pn junction structures, two- or three-dimensional extension of space charge regions enables the usage of highly doped semiconductors, by which on-state resistance can be significantly reduced. This is the first investigation on SiC power devices with such structures. As a typical device, lateral high-voltage MOSFETs have been investigated.
    Effects of doping concentration of each region on breakdown voltage and on-resistance of SiC RESURF (Reduced Surface Field) MOSFETs have been analyzed by using a two-dimensional device simulator. Effective charge at the MOS interface influences the space charge region and thereby breakdown voltage. Optimum dose designing and its guideline have been determined. Double RESURF structure with a pnp layer structure is effective to reduce on-resistance. The breakdown voltage can be increased because the electric field inside the oxide is reduced.
    SiC Lateral RESURF MOSFETs have been fabricated on 10 μm-thick p-type epilayers. Ion implantation was employed to form RESURF, top-p, source, and drain regions. The gate oxide was grown by direct oxidation in N_3O at 1300℃. The typical channel length, RESURF length were 2〜3μm and 20μm, respectively. An original self-aigned process has been developed to fabricate double RESURF MOSFETs. A single-zone double RESURF MOSFET fabricated in this study exhibited a breakdown voltage of 750 V and a low on-resistance of 52 mΩcm^2. The original two-zone double RESURF MOSFET showed characteristics of 1380 V - 66mΩcm^2, which is the pest performance among any lateral MOSFETs ever reported.

  18. High-Voltage, High-Efficiency, High-Speed Power MOSFET Using Wide Bandgap Semiconductor SiC

    Grant number:13555094  2001 - 2002

    KIMOTO Tsunenobu

      More details

    Authorship:Coinvestigator(s) 

    Control of MOS interface, device processing, and fabrication of high-voltage MOSFETs have been investigated by using a wide bandgap semiconductor silicon carbide (SiC), which shows high breakdown field and other excellent physical properties. In control of MOS interface, thermal oxidation at high temperature resulted in the improvement of the MOS quality, and high channel mobilities of 78 cm^2/Vs and 22 cm^2/Vs were obtained for 6H-SiC(OOOl) and 4H-SiC(OOOl) MOSFETs, respectively. 4H-SiC(ll20) and (0338) MOSFETs exhibited a high channel mobility of 30-40 cm^2/Vs. In device processing, thick SiO_2 films deposited by plasma CVD could successfully used as an implantation mask. Short-channel MOSFETs with a channel length of 1 μm could be processed. The electrical activation of implanted dopants was significantly improved by increasing annealing temperature after implantation. The structure of lateral SiC MOSFETs with RESURF (Reduced Surface Field) structure was designed by using a 2D device simulation. The RESURF dose, depth, and the drift layer structure were optimized. SiC lateral RESURF MOSFETs were fabricated on 4H-SiC and 6H-SiC which were grown in our group. The MOSFET showed a very high breakdown voltage of 1 kV and a low on-resistance of 0.1 Ωcm^2. This characteristics outperforms the "Si limit" which is theoretically determined from the material properties, demonstrating the much potential of SiC power devices.

  19. ワイドギャップ半導体ヘテロ界面の電子物性制御とパワーデバイスの高性能化への展開

    Grant number:13750010  2001 - 2002

    須田 淳

      More details

    Authorship:Principal investigator 

    Grant amount:\2100000 ( Direct Cost: \2100000 )

    ワイドギャップ半導体六方晶シリコンカーバイド(SiC)は大きな絶縁破壊電界強度を持つため、既存のシリコン(Si)系半導体パワーデバイスでは理論的に実現不可能な超低損失デバイスを実現可能と期待されている。しかし、シリコン酸化膜(SiO_2)/SiC界面におけるチャネル電子移動度がバルクSiCの電子移動度に比べ極めて小さいため、チャネル抵抗がデバイスの抵抗の大半を占め、デバイスの高性能化を阻んでいる。本研究では、SiO_2に代わる新たな絶縁膜としてSiCと同じ六方晶で、しかも、格子定数がほぼ等しい窒化アルミニウム(AlN)を提案している。窒化アルミニウムとSiCの界面を制御することで、デバイスに利用可能なAlN/SiCヘテロ構造を実現することを目指して研究を進めてきた。今年度得られた結果は以下の通りである。
    1.SiC表面を、構造的観点および化学的観点で制御を行うことで、高品質AlN結晶成長を実現した。すなわちステップ高さの制御と、表面に存在する酸素の完全な除去および表面超構造の発現を行ったSiC上にAlNを成長することで、2次元レイヤーバイレイヤー成長を実現すると共に、結晶性の大幅な改善を実現した。この高品質AIN層の応用としてGaN成長層の為のバッファー層として使用したところ、GaN層の結晶性も大きく向上することを明らかにした。GaN系パワーデバイスへの応用が期待される。
    2.従来用いられてきたSiC(0001)面に加え、無極性面であるSiC(11-20)面上へのAlNの結晶成長を試みた。SiCの結晶方位情報をAlNは引き継いで成長する、すなわち、エピタキシャル成長を実現した。しかし、SiCのポリタイプはAlNに引き継がれず、SiCが6Hポリタイプであるのに対して、AlNは2Hポリタイプ(ウルツ鉱構造)であることが判明した。この現象は結成成長学的に新しい知見であると当時に、GaN系光デバイスで必要とされる、無極性面の実現の1方法を新たに提案するものとして意義がある。

  20. 有機金属分子線エピタキシー法による立方晶窒化ガリウムの結晶成長機構の解明と応用

    Grant number:11750014  1999 - 2000

    奨励研究(A)

    須田 淳

      More details

    Authorship:Principal investigator 

    Grant amount:\1000000 ( Direct Cost: \1000000 )

    トリエチルガリウム(TEGa)とrfプラズマ励起活性窒素(N^*)を原料に用いた有機金属分子線エピタキシャル(MOMBE)成長における、窒化ガリウム(GaN)の結晶成長機構を活用して新規な構造を作製することをめざして研究を進めた。
    立方晶シリコンカーバイド(3C-SiC)の(001)面方位を基板として用いて結晶成長を行ったところ、基板による構造引き込み効果により、サファイア基板上の場合よりもより広い成長条件で立方晶GaNが得られることが分かった。また、3C-SiC基板上においてはGaNの核形成が抑制されることが分かり、連続膜を得るためには低温バッファ層が不可欠であることが判明した。そこで、成長初期の核形成を制御すれば、任意の場所に立方晶の結晶を得ることができると考え、選択成長を試みることにした。
    3C-SiC基板を酸素雰囲気中で1000℃以上に加熱し、表面に酸化膜を形成した後、集束イオンビーム描画装置を用いて、酸化膜の一部を極微細な領域に限って除去し、真空トンネルを通じて直ちに結晶成長装置に搬送、GaNの結晶成長を行った。最適化した成長条件で、酸化膜の除去された開口部のみにGaNの核形成、結晶成長を起こすことに成功した。ただし、有機金属化学気相堆積(MOCVD)法で報告されているような横方向成長は確認されず、微小結晶が密集して存在する結晶成長形態であることが分かった。また、微小結晶は立方晶であり、{111}ファセットを側面に有していることが確認された。成長時間や開口部のサイズ調整などを行うことで、幾何学的に対称性を持つ微小結晶を平面に規則的に並べることができると考えられる。このような構造は、電子エミッタやフォトニック結晶などに応用可能と考えられる。

▼display all

 

Teaching Experience (On-campus) 10

  1. 線形代数学I

    2018

  2. 固体電子工学及び演習

    2018

  3. パワーデバイス工学特論

    2018

  4. 固体電子工学及び演習

    2021

  5. 量子理論

    2021

  6. パワーデバイス工学特論

    2021

  7. 線形代数学I

    2021

  8. 固体電子工学及び演習

    2020

  9. 固体電子工学及び演習

    2020

  10. 線形代数学I

    2019

▼display all