Growth of GaN layers on SiC/Si(111) substrate by molecular beam epitaxy

Abstract

High quality GaN layers were grown by molecular beam epitaxy (MBE), with and without AlN buffer, on SiC/Si(111) substrates obtained by C implantation into Si(111) at 500 °C to avoid amorphization. Thermal annealing at 1150 °C for 6 h produced crystalline SiC layers embedded into the Si(111). The SiC top stoichiometry is controlled by reactive ion etching (RIE), after what, all SiC layers show a fairly flat (4 nm) and specular surface. Photoluminscence spectra reveal that all GaN layers are under tensile biaxial strain of thermal origin. GaN layers grown on stoichiometric SiC have lower mosaicity, but also less photoluminescence efficiency and tensile strain, as compared to GaN on bare non-stoichiometric SiC. This, most likely, relates to changes in microcrystals size and grain boundaries density, that depend strongly on the GaN nucleation process. Despite the partial polycrystalline nature of the SiC/Si(111), the grown GaN quality is as high or even better than that from GaN grown on Si(111).