Stress–strain state and piezoelectric polarization in orthorhombic Ga2O3 thin films depending on growth orientation

Abstract

The experimental data on orientation relationships for halide vapor phase epitaxy (HVPE) κ-Ga2O3 film grown on (0001) α-Al2O3 substrate and the theoretical model that describes growth orientation dependences of stress–strain state and piezoelectric polarization in κ-(AlxGa1-x)2O3 films with orthorhombic crystal structure grown on α-Al2O3 and κ-Al2O3 substrates are presented. Two possibilities for variation in films growth orientation for κ-Ga2O3/α-Al2O3 and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures with inclination axes about either [100] or [010] crystallographic directions are considered. The changes in elastic strain field and piezoelectric polarization in the film caused by the differences in values of lattice parameters, elastic, and piezoelectric constants are demonstrated. The growth planes for κ-Ga2O3/α-Al2O3 and κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures that are characterized by low internal stresses and low or zero values of piezoelectric polarization are found.