Thermal stress in GaN epitaxial layers grown on sapphire substrates

作者：Takahiro Kozawa, Tetsu Kachi, H. Kano, H. Nagase, Norikatsu Koide, Katsuhide Manabe · 发表于：Journal of Applied Physics · 年份：1995 · DOI：10.1063/1.359465 · 被引用次数：298 · 研究领域：GaN-based semiconductor devices and materials、ZnO doping and properties、Acoustic Wave Resonator Technologies

Thermal stress in GaN epitaxial layers with different thicknesses grown on sapphire substrates by metalorganic vapor phase epitaxy using an AlN buffer layer was investigated. Biaxial compressive stress in the GaN layer, due to the difference in the thermal expansion coefficients between GaN and sapphire, was obtained by measuring the curvature of wafer bending, and the observed stress agreed with the calculated stress. In Raman measurements, the E2 phonon peak of GaN was found to shift and broaden with the stress as a consequence of the change of the elastic constants with strain. The frequency shift Δω (in cm−1) was obtained for the first time, given by the relation: Δω=6.2 σ, where the biaxial stress σ is expressed in GPa.