Low temperature deposition of high quality single crystalline AlN thin films on sapphire using highly oriented monolayer MoS2 as a buffer layer

Abstract

AlN films are commonly deposited on sapphire substrates. However, the growth process usually requires high temperature and multi-steps to improve the film quality, due to the large lattice mismatch between the film and substrate. Here we demonstrate that using monolayer MoS2 grown on sapphire as a template, single crystalline AlN films with high crystallinity can be obtained at a much lower growth temperature using helicon sputtering system. The x-ray rocking curve of AlN films prepared on MoS2/sapphire template at 400 °C shows a full width at half maximum of 0.050°, showing a dramatic reduction compared to that of 0.803° for those grown directly on sapphire substrate. The estimated dislocation density of AlN on MoS2/sapphire is decreased to 7.7x107 cm−2, which is comparable to that prepared by metal-organic chemical vapor deposition at high temperatures. The small lattice mismatch between MoS2 and AlN, as well as the polar crystal of monolayer MoS2 apparently improve the quality of AlN films and facilitate AlN formed at lower temperature.