Annealing of the sputtered AlN buffer layer on r‐plane sapphire and its effect on a‐plane GaN crystalline quality

Abstract

We demonstrated how annealing of the sputtered AlN buffer layer (sp‐AlN) on r‐plane sapphire could be used to produce a high‐crystalline‐quality a‐plane GaN (a‐GaN). The sp‐AlN with large grains was confirmed by annealing at 1600 °C in N2 ambient, consequently its crystalline orientation and quality were significantly improved. Moreover, it was found that a‐GaN grown on annealed sp‐AlN showed better crystalline quality, including a reduction of basal stacking fault density, than a‐GaN grown on untreated sp‐AlN (as sputtered). The implication is that the a‐GaN growth method using annealed sp‐AlN is an effective way to obtain high crystalline quality.