Relaxation Mechanism of Thermal Stresses in the Heterostructure of GaN Grown on Sapphire by Vapor Phase Epitaxy
- 1 April 1993
- journal article
- Published by IOP Publishing in Japanese Journal of Applied Physics
- Vol. 32 (4R)
- https://doi.org/10.1143/jjap.32.1528
Abstract
Thermal strains and stresses due to the thermal expansion coefficient difference in GaN(0001)/α-Al2O3(0001) layered structures are studied by varying the film thickness of GaN from 0.6 to 1200 µm. The strain in GaN is greater in films of less than a few microns thickness. It is decreased in films of thickness from several to about a hundred microns, and is almost completely relaxed in those thicker than 100 µm. The stresses and strains in the heterostructure are calculated using a model in which relaxation due to cracking in the sapphire is considered. Three relaxation mechanisms of the thermal strain are found for different film thicknesses as follows: (a) only lattice deformation (20 µm).Keywords
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