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

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.