Improvement of (11-22) GaN on m-plane sapphire with CrN interlayer by using molecular beam epitaxy

This study investigates the crystalline quality, surface, and optical properties of semi-polar GaN (11 2 - 2) grown on m-sapphire substrates with and without a CrN interlayer using molecular beam epitaxy (MBE). The results of the characterization performed by an X-ray diffraction system, scanning electron microscopy and photoluminescence system, all indicate that the crystalline quality, threading dislocation, surface morphology and optical properties of (11 2 - 2) GaN grown with the CrN were superior to those when CrN was not inserted. Details of defect-related emissions of these two samples were observed and investigated in temperature dependent PL measurements, with a low temperature PL spectrum. A weak basal stacking fault related (BSF-related) emission at 3.432 eV was observed in these two samples. In comparison, the BSF-related emission peak as a shoulder to the near band edge (NBE) peaks for the semi-polar GaN grown without CrN was hardly distinguishable at a low temperature.