Stress Relaxation Due to Dislocation Formation in Orthorhombic Ga2O3 Films Grown on Al2O3 Substrates

We analyze the preference of various types of misfit dislocation (MD) formation in film/substrate κ-Ga2O3/α-Al2O3 and κ (AlxGa1–x)2O3/κ-Al2O3 heterostructures. We consider two possibilities for variation in films growth orientation (defined by inclination angle ϑ) for these heterostructures with inclination axes about either [100] or [010] crystallographic directions. We study dependences of the critical film thickness for MD formation on the inclination angle ϑ for heterostructures under consideration. We find the presence of two special orientations (ϑ ~ 26° for [100] heterostructure, ϑ ~ 28° for [010] heterostructure, and ϑ = 90° for both inclination types) of κ-Ga2O3/α-Al2O3 heterostructures, for which the formation of MDs is energetically unfavorable. We show that formation of pure edge MDs is easier for [010] κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures than for [100] heterostructures, and it is vice versa for mixed MDs in these heterostructures.