High-quality InN films on MgO (100) substrates: The key role of 30° in-plane rotation

Abstract

High crystalline layers of InN were grown on MgO(100) substrates by gas source molecular beam epitaxy. Good quality films were obtained by means of an in-plane rotation process induced by the annealing of an InN buffer layer to minimize the misfit between InN and MgO. In situ reflection high-energy electron diffraction showed linear streaky patterns along the [011¯0] azimuth and a superimposed diffraction along the [112¯0] azimuth, which correspond to a 30° α-InN film rotation. This rotation reduces the mismatch at the MgO/InN interface from 19.5% to less than 3.5%, increasing the structural quality, which was analyzed by high-resolution X-ray diffraction and Raman spectroscopy. Only the (0002) c plane diffraction of α-InN was observed and was centered at 2θ = 31.4°. Raman spectroscopy showed two modes corresponding to the hexagonal phase: E1(LO) at 591 cm−1 and E2(high) at 488 cm−1. Hall effect measurements showed a carrier density of 9 × 1018 cm−3 and an electron Hall mobility of 340 cm2/(V s) for a film thickness of 140 nm.