Relaxation mechanism of thermal stresses in the heterostructure of GaN grown on sapphire by vapor phase epitaxy

Thermal strains and stresses due to the thermal expansion coefficient difference in GaN(0001)/α-Al 2 O 3 (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 film...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 32; no. 4; pp. 1528 - 1533
Main Authors HIRAMATSU, K, THEERADETCH DETCHPROHM, AKASAKI, I
Format Journal Article
LanguageEnglish
Published Tokyo Japanese journal of applied physics 01.04.1993
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Summary:Thermal strains and stresses due to the thermal expansion coefficient difference in GaN(0001)/α-Al 2 O 3 (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 (<4 µm), (b) enhancement of interface defects such as “microcracks” and/or dislocations (4-20 µm), and (c) generation of “macrocracks” in sapphire (>20 µm).
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
ObjectType-Feature-1
content type line 23
ISSN:0021-4922
1347-4065
DOI:10.1143/jjap.32.1528