Influence of the nucleation conditions on the quality of AlN layers with high-temperature annealing and regrowth processes

Abstract

Abstract The reduction of dislocation density is a key to improving the performance of AlN-based devices. High-temperature annealing has attracted increasing attention as a method for fabricating high-quality AlN at low cost. We study the influence of the nucleation conditions on the quality of AlN layers with high-temperature annealing and regrowth processes. Higher crystallinity is obtained for samples with a lower nucleation layer growth temperature. The results can be explained in terms of a recrystallization process in which small recrystallized grains without dislocation or strain are generated in the matrix crystal and grow with fusion/annihilation of dislocations at the surrounding grain boundaries. Additional growth of AlN on annealed AlN further improves the crystalline quality and surface flatness. An AlGaN deep-UV light-emitting diode grown on high-temperature annealed AlN shows an external quantum efficiency of 1.9%.