Impact of Cone‐Shape‐Patterned Sapphire Substrate and Temperature on the Epitaxial Growth of p‐GaN via MOCVD

In this paper, the authors report both the effects of the cone-shape-patterned sapphire substrate (CSPSS) and the growth temperature on surface morphology and crystalline quality of the p-GaN layers, grown via metal-organic chemical vapor deposition (MOCVD). Low-temperature GaN buffer and high-temperature undoped GaN (u-GaN) coalescence layers are grown between p-GaN epitaxial film and substrate for all the samples. The time evolution of surface morphology of those films is monitored by scanning electron microscope (SEM) in order to investigate the growth mechanism of films on CSPSS. The compressive stresses in the p-GaN films is also discussed. From atomic force microscopy (AFM) and X-ray diffraction (XRD) results, it is observed that, using CSPSS at a lower temperature (1030 degrees C) significantly reduces the surface roughness and enhances the crystallinity of p-GaN film compared to growth at 1060 degrees C on conventional sapphire substrate. Furthermore, the low resistivity level of 0.05 omega cm and high hole carrier concentration of 1.57 x 10(19) cm(-3) in the p-GaN have been achieved by using CSPSS at lower temperature.