Partial strain relaxation via misfit dislocation generation at heterointerfaces in (Al,In)GaN epitaxial layers grown on semipolar (112¯2) GaN free standing substrates

Abstract

Misfit strain relaxation via misfit dislocation (MD) generation was observed in heteroepitaxially grown (Al,In)GaN layers on free-standing semipolar (112¯2) GaN substrates. Cross-section transmission electron microscope images revealed MD arrays at alloy heterointerfaces, with the MD line direction and Burgers vector parallel to [11¯00] and [112¯0], respectively. The MD structure is consistent with plastic relaxation by dislocation glide on the (0001) plane. Since (0001) is the only slip plane, the plastic relaxation is associated with tilt of the epitaxial (Al,In)GaN layers. The tilt, measured via high-resolution x-ray diffraction, can be used to quantify the relaxation.