RF-MBE growth of a-plane InN on r-plane sapphire with a GaN underlayer

Abstract

a-Plane InN films were grown on r-plane sapphire substrates with GaN underlayers by RF-N 2 plasma molecular beam epitaxy (MBE). X-ray diffraction (XRD) measurements and reflection high-energy electron diffraction (RHEED) observation revealed that the InN films were grown with InN (1 1 2¯ 0)∥GaN (1 1 2¯ 0)∥sapphire (2 2¯ 0 4). We have carried out micro-Raman scattering measurements for a-plane InN film. Raman peaks were observed at 448, 490 and 598 cm −1, which can be identified as the A 1 transversal optical (TO), E 2 (high) and E 1 longitudinal optical (LO) mode phonon, respectively. We also carried out photoluminescence (PL) measurements for a-plane InN film. Strong PL was observed between 0.62 and 0.65 eV, which is the lowest ever reported for InN. It is suggested from the excitation intensity and temperature dependence of the PL spectra that the red shift of the PL peak is due to the Franz–Keldysh effect.