Vapour Phase Epitaxy for GaN Substrates

Published in:
Current issues in crystal growth - Vol. 38, Aa. Vv. (2007), ISBN: 978-88-0971-2, pp. 249-260.
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Abstract:
This paper reviews the current status of the production of freestanding gallium nitride (GaN) substrates for homoepitaxy of GaN devices. The limitations of the use of foreign substrates like sapphire and SiC are discussed. The most important limitations are high dislocation density, significant bowing of the wafers and cracking. While techniques like epitaxial lateral overgrowth (ELOG) can reduce the defect density on foreign substrates, GaN substrates still are highly desired to yield better device performance. Due to a very high equilibrium pressure of nitrogen over GaN and a very low N solubility in a Ga melt classical crystal growth methods fail in producing GaN substrates of technological relevance. The most promising route towards GaN substrates is hydride vapour phase epitaxy (HVPE). The current status of this technology is discussed in this paper.

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