Hydride Vapor Phase Epitaxy Growth of Semipolar ( 101̄3̄ ) GaN on Patterned m-Plane Sapphire

Abstract

We have investigated the hydride vapor-phase epitaxy growth of -oriented GaN thick films on patterned sapphire substrates (PSSs) . From characterization by atomic force microscopy, scanning electron microscopy, double-crystal X-ray diffraction, and photoluminescence (PL), it is determined that the crystalline and optical qualities of GaN epilayers grown on the cylindrical PSS are better than those on the flat sapphire. However, two main crystalline orientations and dominate the GaN epilayers grown on the pyramidal PSS, demonstrating poor quality. After etching in the mixed acids, these GaN films are dotted with oblique pyramids, concurrently lining along the direction, indicative of a typical N-polarity characteristic. Defect-related optical transitions of the GaN epilayers are identified and detailedly discussed in virtue of the temperature-dependent PL. In particular, an anomalous blueshift–redshift transition appears with an increase in temperature for the broad blue luminescence due to the thermal activation of the shallow level.