Misfit dislocation formation via pre-existing threading dislocation glide in (112¯2) semipolar heteroepitaxy

Abstract

Cathodoluminescence (CL) was used to study the onset of mechanical stress relaxation in low indium composition semipolar $(11\overline{2}2)$ In_xGa_1−xN lattice-mismatched layers grown on bulk GaN substrates. Monochromatic CL of short interfacial misfit dislocation (MD) segments showed a single threading dislocation (TD) associated with each MD segment—demonstrating that the initial stage of MD formation in semipolar III-nitride heterostructures proceeded by the bending and glide of pre-existing TDs on the (0001) slip plane. The state of coherency as determined by panchromatic CL is also compared to that determined by x-ray diffraction analysis based on crystallographic epilayer tilt and Matthew-Blakeslee’s critical thickness calculations.