Al 预沉积层对金属有机物化学气相沉积方法在 Si 衬底上生长 AlN 缓冲层和 GaN 外延层的影响

Multilayered films of Al/AlN/GaN were deposited on a Si wafer by metal-organic chemical vapor deposition (MOCVD). The microstructure and crystallinity were characterized by means of optical microscopy (OM), atomic force microscopy (AFM) and X-ray diffractometer (XRD), especially in terms of the mechanisms of nucleation and growth of the produced AlN and GaN films with the variations of trimethylaluminum (TMAl) flow during Al pre-deposition process. It was observed that the pre-deposited Al layer helps the nucleation and growth of AlN film and thereafter improves the quality of GaN film. When a thin Al layer was deposited at low TMAl flow, the quality of the AlN film depends on the competition between the nucleation and growth of the high crystallinity AlN thin film with the deposition of the formed clasters of low crystallinity AlN in the gas phase on the surface of silicon wafer. The quality of the AlN film increases with increasing TMAl flow, inducing the formation of GaN film with better quality. When the Al layer is too thick at high TMAl flow, the quality of the AlN film depends on the competition between the nucleation and growth of the high crystallinity AlN thin film with the meltback-etching of Al-Si on the wafer surface. The quality of the AlN film decreases with increasing TMAl flow, inducing the formation of GaN film with worse quality.