Influence of thermal annealing on GaN buffer layers and the property of subsequent GaN layers grown by metalorganic chemical vapor deposition

We have investigated the influence of low-temperature buffer layer depositi on conditions, such as thickness and thermal annealing time, on the propert ies of the high-temperature GaN growth layer. The surface morphology of the buffer layer after thermal annealing at 1040 degrees C depends on both the thickness of the buffer layer and the annealing time. When a thick buffer layer was used, large trapezoidal growth nuclei were formed after annealing , which led to the poor crystallinity of the GaN growth layer. On the other hand; when a thin buffer layer or a fully annealed thick buffer layer was used, small growth nuclei having a relatively small misorientation were for med, which led to good crystallinity of GaN growth layer. Thus, the thermal annealing time must be optimized, taking the thickness of the buffer layer into the consideration.