Center for Quantum Devices - Journal Articles and Conference Proceedings

Page 1 (12 Items)

1.	Crystallographic Growth Models of Wurtzite-Type Thin Films on 6H-SiC H. Ohsato, K. Wada, T. Kato, C.J. Sun, and M. Razeghi Materials Science Forum Vol. 389-393, no. 2, pp. 1489-1492.-- January 1, 2002 Epitaxial growth of GaN has been tried using various kinds of substrates so far. Of all the substrate, Al₂O₃ has been widely used for the GaN growth. Besides Al₂O₃, SiC is also expected as one of the most suitable substrates for the GaN growth, since SiC has a small mismatch in the lattice parameters with GaN and has good thermal stability under controlled atmospheres during the GaN growth. Both 6H-SiC and GaN having wurtzite structure belong to the same space group (P6₃mc). The lattice parameters are as follows: a=3.08, c=15.08 Å for 6H-SiC and a=3.19, c=5.18 Å for GaN. SiC has two opposite surface polarities along [001] direction. The main objective of our research was to establish a crystallographic growth model of GaN on the (001)6H-SiC with different polarities of Si and C surfaces.
2.	Internal Stress Around Micropipes in 6H-SiC Substrates H. Ohsato, T. Kato, T. Okuda and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 6H-SiC single crystals are expected to be suitable substrates for thin film growth of the wide bandgap semiconductor (GaN, because it has a small lattice mismatch with GaN. Moreover, SiC single crystals are also expected for high-power and high- temperature electric applications because of its wide band gap, high breakdown voltage, high thermal conductivity and high temperature stability. Single crystals with large size used for electronic devices can be grown on seed crystals only by the modified Lely method based on sublimation deposition. But, single crystals have serious defects so called micropipes. These micropipes penetrate almost along the [001] direction. The internal strain around micropipes was investigated using the polarizing optical microscope for the purpose of clarifying the formation mechanisms and decreasing the amount of micropipes. A special interference figure was found around a micropipe under the crossed polars on the polarizing microscope. In this work, the special interference figure around micropipes due to internal stress was explained, and the magnitude and distribution of the stress was measured by means of photoelasticity and the mapping of Raman spectra. reprint
3.	Simultaneous growth of two differently oriented GaN epilayers on (11.0) sapphire (II) a growth model of (00.1) and (10.0) GaN T. Kato, P. Kung, A. Saxler, C.J. Sun, H. Ohsato, M. Razeghi and T. Okuda Journal of Crystal Growth 183-- January 1, 1998
4.	Growth models of GaN thin films based on crystal chemistry: Hexagonal and cubic GaN on Si substrates H. Ohsato and M. Razeghi SPIE Conference, San Jose, CA, -- February 12, 1997
5.	Epitaxial growth models of hexagonal and cubic GaN on (100) Si substrates H. Ohsato, T. Kato, M. Razeghi, and T. Okuda Bulletin of the Ceramic Society of Japan, Ceramics Japan-- January 1, 1997
6.	Morphology of Twinned GaN Grown on (11.0) Sapphire Substrates T. Kato, P. Kung, A. Saxler, C.J. Sun, H. Ohsato, M. Razeghi and T. Okuda Solid-State Electronics 41 (2)-- January 1, 1997
7.	Simultaneous growth of two different oriented GaN epilayers on (11.0) sapphire (I) morphology and orientation T. Kato, H. Ohsato, T. Okuda, P. Kung, A. Saxler, C.J. Sun, and M. Razeghi Journal of Crystal Growth 173-- January 1, 1997
8.	Defects of 6H-SiC substrates made by Acheson's method and by modified Lely's method T. Kato, H. Ohsato, M. Razeghi, and T. Okuda Proceedings - Silicon Carbide and Related Materials Conference, Kyoto, Japan; Institute of Physics Conference Seris 142 (2)-- January 1, 1995
9.	Thermal stability of GaN thin films grown on (0001) Al₂O₃, (0112) Al₂O₃ and (0001)Si 6H-SiC substrates C.J. Sun, P. Kung, A. Saxler, H. Ohsato, E. Bigan, M. Razeghi, and D.K. Gaskill Journal of Applied Physics 76 (1)-- July 1, 1994 Single crystals of GaN were grown on (0001), (0112) Al₂O₃ and (0001)Si 6H‐SiC substrates using an atmospheric pressure metalorganic chemical‐vapor‐deposition reactor. The relationship has been studied between the thermal stability of the GaN films and the substrate’s surface polarity. It appeared that the N‐terminated (0001) GaN surface grown on (0001)Si 6H‐SiC has the most stable surface, followed by the nonpolar (1120) GaN surface grown on (0112) Al₂O₃, while the Ga‐terminated (0001) GaN surface grown on (0001) Al₂O₃ has the least stable surface. This is explained with the difference in the atomic configuration of each of these surfaces which induces a difference in their thermal decomposition. reprint
10.	Crystallography of epitaxial growth of wurtzite-type thin films on sapphire substrates P. Kung, C.J. Sun, A. Saxler, H. Ohsato, and M. Razeghi Journal of Applied Physics 75 (9)-- May 1, 1994 In this article, we present a crystallographic model to describe the epitaxial growth of wurtzite‐type thin films such as gallium nitride (GaN) on different orientations of sapphire (Al2O3) substrates. Through this model, we demonstrate the thin films grown on (00⋅1)Al₂O₃ have a better epilayer‐substrate interface quality than those grown on (01⋅2)Al₂O₃. We also show the epilayer grown on (00⋅1)Al₂O₃ are gallium‐terminated, and both (00⋅1) and (01⋅2) surfaces of sapphire crystals are oxygen‐terminated. reprint
11.	A Crystallographic Model of (001) Aluminum Nitride Epitaxial Thin Film Growth on (001) Sapphire Substrate C.J. Sun, P. Kung, A. Saxler, H. Ohsato, M. Razeghi, and K. Haritos Journal of Applied Physics 75 (8)-- April 15, 1994 A direct comparison of the physical properties of GaN thin films is made as a function of the choice of substrate orientations. Gallium nitride single crystals were grown on (0001) and (011-bar 2) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (011-bar 2) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (011-bar 2) sapphire. The results of this study show better physical properties of GaN thin films achieved on (011-bar 2) sapphire. reprint
12.	Al_xGa_1-xN Grown on (001) and (012) Sapphire C.J. Sun, P. Kung, A. Saxler, H. Ohsato, and M. Razeghi Proceedings of the 5th International Conference on Silicon Carbide and Related Materials, Washington, DC-- November 1, 1993

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