MBE growth of hexagonal InN films on sapphire with different initial growth stages

Pure hexagonal InN films were deposited on Al2O3 (0001) substrates by plasm a assisted molecular beam epitaxy at various temperatures from 300 to 500 d egrees C. The temperature of 470 degrees C has been found to be the maximal one allowing In-droplet-free InN growth at a growth rate of 0.2 to 0.3 mu m/h. Reflection high energy electron diffraction, scanning electron microsc opy, X-ray diffraction, Raman scattering, and Hall-effect measurements are used to investigate the film properties as dependent on initial growth stag es,The most effective initial stage involving high temperature annealing of a 15 nm thick InN buffer grown at low temperature results in significantly improved structural properties of the following InN layer. In spite of the high electron concentration of the order of 10(20) cm(-3), the room temper ature Hall mobility up to 600 cm(2)/Vs has been demonstrated.