Dependence of the stress–temperature coefficient on dislocation density

Date

2004-02-15

Authors

Temkin, H.
Faleev, N.
Holtz, Mark
Ahmad, I.

Journal Title

Journal ISSN

Volume Title

Publisher

American Institute of Physics

Abstract

We report measurements of stress in GaN epitaxial layers grown on 6H–SiC and a-Al2O3 substrates. Biaxial stresses span 11.0 GPa ~tensile! to 21.2 GPa ~compressive!. Stress determined from curvature measurements, obtained using phase-shift interferometry ~PSI! microscopy, compare well with measurements using accepted techniques of x-ray diffraction ~XRD! and Raman spectroscopy. Correlation between XRD and Raman measurements of the E2 2 phonon gives a Raman-stress factor of 23.460.3 cm21/GPa. We apply PSI microscopy for temperature dependent stress measurements of the GaN films. Variations found in the stress–temperature coefficient correlate well with threading dislocation densities. We develop a phenomenological model which describes the thermal stress of the epitaxial GaN as a superposition of that for ideal GaN and the free volume existing in the layers due to the threading dislocations. The model describes well the observed dependence.

Description

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Citation

Dependence of the stress--temperature coefficient on dislocation density in epitaxial GaN grown on alpha-Al[sub 2]O[sub 3] and 6H--SiC substrates, I. Ahmad, M. Holtz, N. N. Faleev, and H. Temkin, J. Appl. Phys. 95, 1692 (2004), DOI:10.1063/1.1637707

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