MOCVD growth and characterization of GaN films with composite intermediate layer buffer on Si substrate

Abstract

GaN thin films have been grown on Si(001) substrate with specially designed composite intermediate layers (CIL) consisting of an ultrathin amorphous silicon layer and a GaN/AlxGa1-xN multi-layered buffer by low pressure metal-organic chemical vapor deposition (MOCVD). The improved film quality has been obtained from adjusting the parameters and redesigning the buffer layer structures. These were verified from different materials characterization measurements. XRD patterns showed strong and narrow (0002) and (0004) peaks of wurtzite phase GaN, and no cubic or other phase features. Room temperature photoluminescence showed strong GaN near band edge emission at 3.42 eV with almost no deep defect emission features to be detected from the improved quality films. Raman scattering and infrared spectroscopy exhibited phonon and lattice vibration modes characteristic of wurtzite GaN with no modes related to cubic or other structural phase. Scanning electron microscopy reveals the polycrystalline structure with large grain sizes near 2 μm in these films.