Study of dual nitridation processes in growth of non-polar a-plane AlGaN epi-layers

The effect of dual nitridation processes for both r-plane sapphire and low temperature-grown AlN (LT-AlN) nucleation layer on non-polar a-plane AlGaN epi-layer was studied intensively. A root-mean-square value as small as 1.54 nm for a-plane Al0.53Ga0.47N epi-layer was achieved. It was revealed that the generation of AlN grains as well as the coalescence and recrystallization of LT-AlN islands were the key factors for growing a-plane AlGaN epi-layers with smooth surface morphology. Meanwhile, the evolution of surface morphology with varied nitridation processes and the mechanisms for improving surface morphology of a-plane AlGaN epi-layers were also investigated.