High-quality InN films on MgO (100) substrates: the key role of 30 degrees 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 [01 (1) over bar0] azimuth and a superimposed diffraction along the [11 (2) over bar0] azimuth, which correspond to a 30 degrees alpha-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 a-InN was observed and was centered at 2 theta = 31.4 degrees. 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 x 10(18) cm(-3) and an electron Hall mobility of 340 cm (2)/(V s) for a film thickness of 140 nm."