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

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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.