Influence of the nucleation conditions on the quality of AlN layers with higherature annealing and regrowth processes

Abstract

The reduction of dislocation density is a key to improving the performance of AlN-based devices. Higherature 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 higherature 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 higherature annealed AlN shows an external quantum efficiency of 1.9%.