High Quality Al-Polar AlN Growth on (0001) Sapphire Using Polarity-Selective Thermal Etching by High Temperature Metalorganic Chemical Vapor Deposition

In this study, we suggest a polarity-selective in-situ thermal etching and re-growth process for the fabrication of high quality Al terminated AlN epilayers by high temperature metalorganic chemical vapor deposition. Mixed-polar AlN layers grown on a thin (5 nm) buffer layer at a high temperature (950 degrees C) exhibited high crystalline quality. Surface morphologies of in-situ thermally etched AlN layers depended on the grain size and distance between grains. Increasing the initial grain size and diminishing the space between grains increased etching depth and width. During re-growth, threading dislocations were bent and annihilated in the vicinity of voids, which were formed by lateral growth of Al-polar AlN regions after thermal etching. Finally, a high quality Al-polar AlN template, as verified by an aqueous KOH solution, was successfully fabricated.