Optical and Electrical Properties of Al_(1-x)In_xN Films Grown on Sapphire (0001) by Plasma Source Molecular Beam Epitaxy

摘要

A series of epitaxial In_xAl_(1-x)N alloy films (thickness ～ 150 nm) with 0 ≤ x ≤ 1.0 were grown by Plasma Source Molecular Beam Epitaxy (PSMBE) on sapphire (0001) at a low substrate temperature of 375℃. X-ray diffraction (XRD) measurements confirm a c-axis oriented epitaxial growth of alloy films without any alloy segregation. However, the degree of crystalline mosaicity, compositional fluctuation and surface roughness, all increase with increasing x. The direct energy band gap of alloy films were determined using optical (UV-VIS) transmission and reflection measurements. The observed bowing of the direct gap versus x plot, when compared to the theoretical prediction, is less pronounced than seen in earlier studies reported in literature. Electrical resistivity and Hall effect measurements show n-type electrical conductivity in these alloys with carrier concentrations ～10~(19)-10~(20) cm~(-3) for x > 0.5.