Verification of the Hypothesis on the Thermoelastic Nature of Deformation of a (0001)gan Layer Grown on the Sapphire a -Cut

The deformation of a (0001)GaN epitaxial layer on the (11\(\bar {2}\)0) sapphire a-cut is studied by X-ray diffractometry. Anisotropic-layer deformation is calculated by reference data on the thermal expansion coefficients of gallium nitride and sapphire. A comparison of the calculated and experimental deformation confirms the hypothesis on the thermoelastic character of GaN deformation on the sapphire a-cut. This result makes it possible, in particular, to assess theoretically the elastic deformation and piezoelectric field in pseudomorphic heterostructures with GaN layers on the sapphire a-cut as a virtual substrate or a buffer layer.