Faculty Profiles - SUDA Jun

Papers - SUDA Jun

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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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2018 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) 2018

Comparison between GaN and SiC From the viewpoint of vertical power devices

Suda J.

CS MANTECH 2018 - 2018 International Conference on Compound Semiconductor Manufacturing Technology 2018

Language：English Publishing type：Research paper (scientific journal) Publisher：CS MANTECH 2018 - 2018 International Conference on Compound Semiconductor Manufacturing Technology

Thanks to superior materials properties, GaN has great potential as the next-generation power devices. The author will discuss challenges for GaN vertical devices by referring SiC technologies, which has over 20 years history.

Scopus

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

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

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

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

Web of Science

Scopus

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

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

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

Language：English 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

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Papers - SUDA Jun