Pre-treatment of low temperature GaN buffer layer deposited on AlN/Si substrate by hydride vapor phase epitaxy

We investigated the effects of pre-treatments of a low temperature GaN (LT-GaN) buffer layer on its properties, and of a thick GaN film to improve its qualities. Pre-treatment was performed by annealing the LT-GaN buffer layer under different conditions including different ambient gases (NH3 and N2) and temperatures. We found that the pre-treatments of LT-GaN strongly affected surface morphology, crystallinity and optical property of GaN. Crystallinity and optical property of the pre-treated LT-GaN were improved as compared with as-deposited LT-GaN buffer layer. Thick GaN layers with high quality were also obtained by pre-treatment of LT-GaN buffer layer. Surface roughness, morphology and chemistry of the pre-treated LT-GaN buffer layer and thick GaN film on AlN/Si substrate were examined by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) respectively. Optical characteristics and crystallinity of LT-GaN were measured by low temperature photoluminescence (PL), and X-ray diffractometry (XRD), respectively.