Evaluation of Misfit Relaxation in α-Ga2O3 Epitaxial Growth on α-Al2O3 Substrate

Abstract

Corundum-structured α-Ga2O3 epitaxial thin films were grown on c-plane α-Al2O3 (sapphire) substrates by a mist chemical vapor deposition method. To reveal the defect structures, the α-Ga2O3 film was observed by high-resolution transmission electron microscopy (TEM). We found that the α-Ga2O3 thin film was in-plane compressive stressed from the α-Al2O3 substrate. Although misfit dislocations were periodically generated at the α-Ga2O3/α-Al2O3 interface owing to the large lattice mismatches between α-Ga2O3 and α-Al2O3, 3.54% (c-axis) and 4.81% (a-axis), most of the misfit dislocations did not thread through the layer. An extra-half plane was {2̄110} consisting only of Ga. Screw dislocations were not confirmed, i.e., the density was under 107 cm-2. The threading dislocation density was 7 ×1010 cm-2.