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

Corundum-structured α-Ga 2 O 3 epitaxial thin films were grown on c -plane α-Al 2 O 3 (sapphire) substrates by a mist chemical vapor deposition method. To reveal the defect structures, the α-Ga 2 O 3 film was observed by high-resolution transmission electron microscopy (TEM). We found that the α-Ga 2 O 3 thin film was in-plane compressive stressed from the α-Al 2 O 3 substrate. Although misfit dislocations were periodically generated at the α-Ga 2 O 3 /α-Al 2 O 3 interface owing to the large lattice mismatches between α-Ga 2 O 3 and α-Al 2 O 3 , 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 10 7 cm -2 . The threading dislocation density was 7 ×10 10 cm -2 .