Investigation of nucleation and intermixing at hetero-interface in III-Nitride-4H-SiC structures

III-Nitride/SiC heterostructure devices are a promising approach for improving the performance of SiC devices such as bipolar transistors and avalanche photodiodes. However, the performance of these devices should critically depend on the properties of the hetero-interface that will likely lie within an active region of the device and impact carrier transport. Importantly, intermixing at the hetero-interface can effect doping profiles in these structures as constituent atoms of each semiconductor act as a dopant in the other. In this paper we explore the impact of in situ substrate preparation and migration enhanced epitaxy (MEE) on the nucleation and impurity concentration of thin AlN films grown by plasma-assisted molecular beam epitaxy on 4H-SiC. The surface morphology of the samples were examined by atomic force microscopy and the composition of the films were studies by secondary ion mass spectroscopy (SIMS) and depth profiling x-ray photoemission spectroscopy (XPS). The MEE approach promotes the nucleation of AlN growth on SiC in a 2D mode while suppressing the migration of Al into SiC. Active N that leaks around the closed shutter during in-situ preparation prevents the nucleation of AlN in a 2D growth mode at lower substrate temperatures that is attributed to GaN island formation at the hetero-interface.