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

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 (RF-IWE). 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.