Faculty Profiles - SUDA Jun

Papers - SUDA Jun

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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

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

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

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

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

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

4H-SiC MISFETs with nitrogen-containing insulators

Noborio Masato, Suda Jun, Beljakowa Svetlana, Krieger Michael, Kimoto Tsunenobu

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Vol. 206 ( 10 ) page： 2374 - 2390 2009.10

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

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

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

Accurate measurements of second-order nonlinear optical coefficients of 6H and 4H silicon carbide

Sato Hiroaki, Abe Makoto, Shoji Ichiro, Suda Jun, Kondo Takashi

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS Vol. 26 ( 10 ) page： 1892 - 1896 2009.10

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

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

In situ Gravimetric Monitoring of Thermal Decomposition and Hydrogen Etching Rates of 6H-SiC(0001) Si Face

Akiyama Kazuhiro, Ishii Yasuhiro, Abe Sohei, Murakami Hisashi, Kumagai Yoshinao, Okumura Hironori, Kimoto Tsunenobu, Suda Jun, Koukitu Akinori

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 48 ( 9 ) page： 0955051 - 0955054 2009.9

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

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

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

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

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

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

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

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

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

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

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

Triple Shockley type stacking faults in 4H-SiC epilayers

Feng Gan, Suda Jun, Kimoto Tsunenobu

APPLIED PHYSICS LETTERS Vol. 94 ( 9 ) 2009.3

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

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

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

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

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

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

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

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

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

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

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

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

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

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