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

采用金属有机物化学气相沉积法(MOCVD)在硅(Si)衬底制备铝/氮化铝/氮化镓(Al/AlN/GaN)多层薄膜，使用光学显微镜(OM)、原子力显微镜(AFM)、X射线衍射(XRD)等手段表征AlN和GaN薄膜的微观结构和晶体质量，研究了TMAl流量对AlN薄膜和GaN薄膜的形核和生长机制的影响。结果表明，预沉积Al层能促进AlN的形核和生长，进而提高GaN外延层的薄膜质量。TMAl流量太低则预沉积Al层不充分，AlN缓冲层的质量取决于由形核长大的高结晶度AlN薄膜与在气氛中团聚长大并沉积的低结晶度AlN薄膜之间的竞争，AlN薄膜的质量随着TMAl流量的升高而提高，GaN薄膜的质量也随之提高。TMAl流量太高则预沉积Al层过厚，AlN缓冲层的质量取决于由形核长大的高结晶度AlN薄膜与Al-Si回融蚀刻之间的竞争，AlN薄膜的质量随着TMAl流量的升高而降低，GaN薄膜的质量也随之降低。

Effect of Pre-deposited Al Layer on Growth of AlN Buffer Layer and GaN Film on Si Substrate by Metal-organic Chemical Vapor Deposition

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.