Faculty Profiles - SUDA Jun

Papers - SUDA Jun

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Molecular beam epitaxy of GaN on lattice-matched zirconium diboride substrates using low-temperature GaN and ALN nucleation layers

Armitage R., Suda J., Kimoto T.

Proceedings - Electrochemical Society Vol. 6 page： 484 - 495 2004.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings - Electrochemical Society

GaN epilayers have been grown on lattice-matched ZrB2 substrates by rf-molecular beam epitaxy using a two-step method with low-temperature GaN or AlN employed as the nucleation layer. N-polarity was always obtained for GaN nucleation layers, while Ga-polarity could be obtained with AlN nucleation layers under certain conditions. The characteristics of N-polar GaN epilayers were found to strongly depend on the Ga/N ratio during initial nucleation. Remarkably smooth morphologies (rms <0.5 nm over 10 μm2) with atomic steps up to several μm long were obtained for layers with N-excess nucleation conditions. Ga-excess nucleation conditions resulted in better x-ray diffraction characteristics, but the morphology showed a subgrain structure and increased roughness (rms 1-2 nm). Typical ω-scan values for Ga-excess nucleation were in the range 400-500 arcsec and 750-860 arcsec for the (002) and (104) reflections, respectively. Possible reasons for the high dislocation density despite the good lattice match of ZrB2 are discussed.

Molecular-beam epitaxy of III-N on novel ZrB<inf>2</inf> substrates

Suda J.

Proceedings of SPIE - The International Society for Optical Engineering Vol. 5349 page： 397 - 407 2004.8

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

Electrically conductive zirconium diboride (ZrB2) is a promising lattice-matched substrate for GaN-based nitride semiconductors. In this paper, important properties of ZrB2 as a substrate for nitrides, such as, thermal expansion coefficient, thermal conductivity, optical reflectivity and cleavage, are reviewed. Then, heteroepitaxial growth of GaN and AlN on the substrate by molecular-beam epitaxy (MBE) are discussed. Direct growth and two-step growth using low-temperature GaN nucleation layers as well as characterization of the surface condition of ZrB2 substrates by X-ray photoelectron spectroscopy (XPS) and the effect of surface treatment on grown layers are presented.

DOI： 10.1117/12.540326

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

High channel mobilities of MOSFETs on highly-doped 4H-SiC (11-20) face by oxidation in N<inf>2</inf>O ambient

Kanzaki Y., Kinbara H., Kosugi H., Suda J., Kimoto T., Matsunami H.

Materials Science Forum Vol. 457-460 ( II ) page： 1429 - 1432 2004

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

Planar n-channel MOSFETs have been fabricated on 4H-SiC (11-20), (0001) and (000-1) faces by using oxidation in N2O ambient. The relationship between the MOSFET performance and the acceptor concentration (7×10 15-2×1017 cm-3) of epilayers has been investigated. 4H-SiC (11-20) MOSFETs have shown a high effective channel mobility of 70 cm2/Vs at a 2×1016 cm-3 doping, and 54 cm2/Vs at 2×1017 cm-3. Short-channel effects have been also investigated.

Towards high-quality AlN/SiC hetero-interface by controlling initial processes in molecular-beam epitaxy

Onojima N., Kaido J., Suda J., Kimoto T., Matsunami H.

Materials Science Forum Vol. 457-460 ( II ) page： 1569 - 1572 2004

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

The electronic properties of AlN/SiC hetero-interface were investigated by using Al/AlN/4H-SiC MIS capacitors. Single crystalline AlN was grown on n-type 8° off-axis 4H-SiC (0001) epilayers via plasma-assisted molecular-beam epitaxy (PA-MBE). The C-V characteristics revealed that the initial pre-irradiation of atomic nitrogen (N*) before AlN growth strongly affected the electronic properties of AlN/SiC interface, which probably attributed to the atomic arrangement of Al, N, Si and C at the interface. A noticeably small value of interface state density (Dit), such as 3×1011 cm-2eV-1 at Ec-0.2 eV, was obtained for the N* pre-irradiated interface.

DOI： 10.4028/www.scientific.net/msf.457-460.1569

4H-polytype AlN grown on 4H-SiC(11(2)over-bar0) substrate by polytype replication

Onojima N, Suda J, Kimoto T, Matsunami H

APPLIED PHYSICS LETTERS Vol. 83 ( 25 ) page： 5208 - 5210 2003.12

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

The growth of aluminum nitride (AlN) on a 4H-SiC(112̄0) substrate, which has a different stacking structure compared to 6H-SiC was studied. 4H-AlN was grown on the 4H-SoC(112̄0) substrate owing to the atomic-template effect, i.e., polytype reduction. The FWHM of XRC (112̄0) diffraction for the 4H-AlN epilayer was as small as 90 arc sec. The results show that the excellent crystalline quality is probably owing to the polytype matching between the 4H-AlN epilayer and the 4H-SiC substrate.

DOI： 10.1063/1.1636533

High-quality AlN by initial layer-by-layer growth on surface-controlled 4H-SiC(0001) substrate

Onojima N, Suda J, Matsunami H

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS Vol. 42 ( 5A ) page： L445 - L447 2003.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 2: Letters

The initial layer-by-layer growth of AlN was realized on a surface-controlled 4H-SiC(0001) substrate using plasma-assisted molecular-beam epitaxy (PA-MBE). To achieve initial two-dimensional (2D) growth, the control of SiC surface chemistry is very important as well as that of surface flatness. The effect of SiC preparation on the surface structure and chemical composition was investigated by using reflection high-energy electron diffraction (RHEED) and in situ X-ray photoelectron spectroscopy (XPS). The initial growth mode of AlN was strongly influenced by the removal of residual oxygen atoms from the SiC surface. Symmetrical and asymmetrical X-ray rocking curve (XRC) measurements revealed that initial 2D growth was essential to obtain the excellent crystalline quality of AlN layer.

DOI： 10.1143/JJAP.42.L445

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

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

Using epitaxial multiple p-n junction structures of 4H-SiC, lateral super junction diodes were fabricated for the first time. The breakdown voltage of the device was 400 V, which is more than 3 × higher than the theoretical value calculated for a device with uniformly-doped drift layer (130 V), indicating the effective operation of super junction structure.

DOI： 10.1109/LED.2003.812561

ZrB2 substrate for nitride semiconductors

Kinoshita H, Otani S, Kamiyama S, Amano H, Akasaki I, Suda J, Matsunami H

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS Vol. 42 ( 4B ) page： 2260 - 2264 2003.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

Zirconium diboride (ZrB2) has excellent properties as an electrically conductive substrate for nitride semiconductors. In this paper, the bulk growth of ZrB2 by a floating-zone method and some properties of ZrB2, together with a brief summary of heteroepitaxial growth of gallium nitride (GaN) by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE), are presented. By optimizing the bulk growth conditions, a 20-mm-diameter ZrB2 single crystal was obtained. The cleavage direction of the ZrB2 (0001) substrate was confirmed to be parallel to [112̄0], which is parallel to that of GaN (0001). Epitaxial growth by both MBE and MOVPE was demonstrated. The grown n-type GaN/ZrB2 structure exhibited ohmic-like current-voltage behavior. These results indicate that ZrB2 has potential for application to the substrate for nitride semiconductors.

DOI： 10.1143/JJAP.42.2260

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

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi C: Conferences

The surface pretreatment of SiC substrate for AlN heteroepitaxial growth was investigated to realize initial two-dimensional (2D) layer-by-layer growth. AlN layers were grown on atomically flat SiC (0001) substrates by plasma-assisted molecular-beam epitaxy (PA-MBE). To achieve initial 2D growth, the control of SiC surface chemistry was very important as well as that of surface flatness. Owing to Ga deposition on the SiC surface and subsequent flash-off, an oxygen-free (V3 × V3) R30° surface structure was achieved, and initial 2D growth with an evident RHEED intensity oscillation was demonstrated. The initial growth mode of AlN closely correlated with the crystalline quality of AlN layer. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200303358

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi C: Conferences

Non-polar AlN epitaxial growth on SiC substrates with the (11-20) face, which is parallel to the 〈0001〉 direction, has been investigated. AlN(11-20) epilayers were grown on 6H- and 4H-SiC(11-20) substrates by molecular-beam epitaxy (MBE) using elemental Al and rf plasma-excited nitrogen. The crystalline structure of the AlN layer was strongly influenced by the stacking structure of the SiC substrate. A considerably smooth AlN(11-20) layer with an rms roughness of 0.3 nm was obtained on the 4H-SiC(11-20) substrate. From the results of X-ray diffraction (XRD), the superior crystalline quality of the AlN(11-20) layer on the 4H-SiC(11-20) substrate was clearly shown. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200303396

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

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

Either step-flow or layer-by-layer growth for AlN on SiC (0001) substrates

Suda J., Onojima N., Kimoto T., Matsunami H.

Materials Research Society Symposium - Proceedings Vol. 798 page： 311 - 316 2003

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

AlN was grown on 4H- or 6H-SiC (0001) on-axis substrates by plasma-assisted molecular beam epitaxy. By utilizing optimized SiC surface pretreatment, RHEED oscillations just after the growth of AlN were obtained with high reproducibility. This study focused on the growth kinetics of AlN and the correlation between kinetics and the crystalline quality of the grown layers. It was found that the growth mode changed from layer-by-layer to step-flow for high growth temperatures, while for lower temperatures the layer-by-layer growth mode persisted. The mechanism responsible for the change in growth mode is discussed. Symmetrical (0002) and asymmetrical (01-14) x-ray rocking curve measurements were carried out to evaluate the crystalline quality. For the (0002) peak, both high-temperature and low-temperature grown layers showed almost the same FWHM values. On the other hand, for the (01-14) peak, the FWHM of low-temperature grown AlN was much smaller (180 arcsec) than that of the high-temperature grown AlN (450 arcsec).

DOI： 10.1557/proc-798-y3.4

SiC Lateral Super-Junction Diodes Fabricated by Epitaxial Growth

Miura M., Nakamura S.I., Suda J., Kimoto T., Matsunami H.

Materials Science Forum Vol. 433-436 page： 859 - 862 2003

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

Lateral super junction diodes were fabricated using epitaxial multiple pn junction structures of 4H-SiC. The diodes showed very high on-state current densities of 500 A/cm2 at 3.9V and 1000 A/cm2 at 5.0V were obtained, and the corresponding specific on-state resistance of 2.1 mΩcm2. Even without the aid of conductivity modulation, a specific on-state resistance of 4.2 mΩcm2 was obtained, showing an extremely low value as lateral devices. The maximum breakdown voltage of the diodes was 400V, which is more than three times higher than the theoretical value calculated for a lateral p+n diode with a uniformly-doped drift region (130 V), indicating the effective operation of super junction structure made of SiC.

DOI： 10.4028/www.scientific.net/msf.433-436.859

Surface control of ZrB<inf>2</inf> (0001) substrate for molecular-beam epitaxy of GaN

Suda J., Yamashita H., Armitage R., Kimoto T., Matsunami H.

Materials Research Society Symposium - Proceedings Vol. 798 page： 369 - 374 2003

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

Zirconium diboride (ZrB2) is a promising lattice-matched substrate for GaN-based materials. A key issue to realize high-quality heteroepitaxial growth is preparation of the substrate surface. The ZrB 2 surface was studied by x-ray photoemission spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). XPS results indicated the presence of both ZrO2 and ZrB2 on the as-received substrate surface. Thermal cleaning at 1000°C in ultra-high vacuum, Ar + ion sputtering, and wet chemical treatments were examined as surface preparation methods. After treatment with HF acid, the O peak intensity was much reduced. The combination of HF treatment and thermal cleaning resulted in sharp and intense RHEED from the ZrB2 surface. GaN grown on the surface by molecular-beam epitaxy exhibited intense photoluminescence, suggesting that this treatment is effective to obtain high-quality GaN on ZrB2 substrates.

DOI： 10.1557/proc-798-y10.65

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

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

A high-temperature HCl-gas etching technique followed by chemical treatment as a SiC substrate pretreatment, which resulted in 1 × 1 reconstruction with an atomically flat surface was proposed. The effects of SiC surface reconstruction on the lattice relaxation of AlN buffer layers and the crystalline quality of GaN layers were investigated. The GaN layers grown on the AlN buffer layer demonstrated the narrowest x-ray rocking curve (XRC) (0002) diffraction of 70 arcsec and 107 cm-2 screw-type dislocation density, which is two orders of magnitude smaller than that of GaN grown on as-received substrates.

DOI： 10.1063/1.1533855

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 2: Letters

AlN epitaxial growth on 6H-SiC substrates with the (112̄0) face, which is parallel to the <0001> direction, has been investigated. AlN epitaxial layers were grown by molecular-beam epitaxy (MBE) using elemental Al and rf plasma-excited nitrogen (N*). The surface roughness of the AlN layers was relatively small (rms roughness of 0.98 nm). From the results of reflection high-energy electron diffraction (RHEED), AlN layers on 6H-SiC (112̄0) substrates were revealed to be grown toward the [112̄0] direction, not toward the [0001] direction. AlN and 6H-SiC (112̄0) had an exact epitaxial relationship, i.e., [112̄0]AlN ∥ [112̄0]SiC and [0001]AlN ∥ [0001]SiC. The polytype of the AlN layer was also discussed based on the results of microscopic Raman scattering spectroscopy.

DOI： 10.1143/JJAP.41.L1348

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

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