Evolution of AlN buffer layers on silicon and effects on the properties of epitaxial GaN films

摘要

The morphological evolution of AlN buffer layers grown on (111) silicon at high-temperature has been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The structure and morphology of subsequently grown GaN films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements. It was found that even though thicker AlN buffer layers are the poor single crystal with some defects like mis-oriented domains, stacking faults, they provide better templates for subsequent growth of GaN films with better crystalline and optical properties, compared to the GaN grown on a thin AlN buffer layer. To prevent the formation of SiN_x layers at the interface, TMA was flowed for several seconds prior to the introduction of ammonia into the chamber. The AFM result showed that quasi 2-dimensional growth was quickly achieved for the AlN buffer layer with TMA pre-treatment.