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Effect of SiC‐on‐Si template residual stress on GaN residual stress and crystal quality
Author(s) -
Chai Jessica,
Walker Glenn,
Wang Li,
Massoubre David,
Iacopi Alan
Publication year - 2016
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201552626
Subject(s) - materials science , residual stress , overlayer , ultimate tensile strength , stress (linguistics) , composite material , crystal (programming language) , condensed matter physics , computer science , linguistics , philosophy , physics , programming language
The thermal expansion coefficient mismatch between GaN and SiC is lower than between GaN and Si. However it is usually observed that GaN on SiC/Si templates has higher tensile stress than GaN directly on Si. To provide an insight into the relationship between SiC template residual stress and GaN overlayer residual stress and crystal quality, we have analyzed the in‐plane residual stress gradient present in GaN/SiC microstructure arrays of various dimensions and shapes using micro‐Raman spectroscopy. It was found that the GaN overlayer residual stress is directly proportional to the SiC buffer layer residual stress. GaN films with lower residual stress also resulted in GaN films with improved crystal quality. Our study shows that the frequently encountered problems of high tensile stress in GaN films deposited on SiC templates is due to the high tensile residual stress in the SiC layers. The poorer GaN crystal quality deposited on SiC templates reported in literature is also likely due to the high tensile stress in the SiC templates. In order to grow GaN films with sufficient compressive stress and crystal quality for subsequent device processing, it is crucial to reduce the high tensile stress present in the SiC templates.