Growth and spectroscopic characterization of epitaxial dielectrics on SiC

SiC has attracted much attention as a promising wide-bandgap semiconductor material due to its excellent physical and electrical properties. In SiC-based devises, inclusion of an AlN buffer layer improves the performance due to its good lattice match with SiC substrate and relatively low misfit with the III- nitride layers. In this work, we demonstrate the deposition of HfO$_2$, a well known high-k gate dielectric material for silicon based devices, by an atomic layer deposition process on SiC and AlN/SiC stacks. During the thin-film growth, the crystallinity of the epitaxial layers is monitored by in-situ reflection high-energy electron diffraction (RHEED) and the thin film composition is characterized by in-situ x-ray photoelectron spectroscopy (XPS). To examine the characteristic electrical properties, capacitance-voltage and current-voltage measurements are performed on the metal-insulator-semiconductor (MIS) capacitors. The correlation between growth conditions, stoichiometry and crystallinity of the eptaxial layer, and device performance will be discussed. Finally, we present first- principle calculations of the valence band structures of AlN and SiC as well as band alignment at the interface, in comparison with the experimentally determined band alignment by XPS.