High Quality GaN Films Grown on Sapphire by RF-MBE without Low Temperature Buffer Layers

Abstract

To improve the quality of grown GaN films, a low temperature (LT) buffer layer as a nucleation layer between GaN films and sapphire substrates is the most common way to solve the serve large lattice mismatch between GaN and sapphire. With a suitable Ga/N ratio, high quality GaN films can be grown directly on the sapphire without using any low temperature buffer layers by radio frequency molecular beam epitaxy (RFMBE). The 0.753 nm rms surface roughness and 5.4 arcmin full-width at the half-maximum (FWHM) of XRD can be achieved by optimizing the Ga/N ratio without any low temperature buffer layers. As shown in the results, the surface roughnesses and XRD FWHM of epilayers are a function of Ga flux at the same substrate temperature and N2 flow rate.