Investigation of crystallographic tilting in GaSb/GaAs heteroepitaxial structure by high-resolution X-ray diffraction

GaSb epilayers were grown on GaAs(0 0 1) vicinal substrate misoriented towards (1 1 1) plane by solid-source molecular beam epitaxy (MBE). The relative tilt between GaSb epilayer and GaAs substrate was studied using high-resolution X-ray diffraction (HRXRD). It was demonstrated that the tilt of the 30 nm thick GaSb film was 0.32°, which was a simple geometrical consequence of 7.8% lattice mismatch. For the 1000 nm thick film, tilt rose to 0.45°, and the increase of tilt was the result of the forming of 60° misfit dislocations (MDs). In contrast to the phenomenon in low-misfit heteroepitaxy system, tilts induced by 60° MDs in our samples were positive (i.e. away from the surface normal) and we attributed the diversity to the different formation mechanisms of 60° MDs. The tilt study gave us another way to investigate the type and the formation mechanism of the MDs.