Epilayer lattice tilt was observed, using X-ray diffraction, in hetero-epitaxial AlGaN and InGaN films grown onto (11•2) semipolar GaN substrates. Transmission electron microscopy revealed that the epilayer tilt was caused by interfacial misfit dislocations, with Burgers vectors of a/3[11•0], that glided on the (00•1) basal plane; inclined at about 58° with respect to (11•2). The dislocation lines were parallel to [11•0]; consistent with the anisotropy of the tilt observed in X-ray scans parallel to the orthogonal in-plane directions. The dislocations had an in-plane Burgers vector component that relieved misfit strain, and a perpendicular component which was responsible for the lattice tilt. The dislocation densities which were predicted from the tilt agreed well with transmission electron microscopic measurements.

Lattice Tilt and Misfit Dislocations in (1122) Semipolar GaN Heteroepitaxy. E.C.Young, F.Wu, A.E.Romanov, A.Tyagi, C.S.Gallinat, S.P.DenBaars, S.Nakamura, J.S.Speck: Applied Physics Express, 2010, 3[1], 011004