Photoemission Study on Chemical Bonding Features and Electronic Defect States of Thermally-Grown SiO2/4H-SiC Structure

Abstract

Depth analysis of thermally grown SiO2/4H-SiC structure has been conducted systematically by high resolution x-ray photoelectron spectroscopy (XPS) and total photoelectron yield spectroscopy (PYS) to gain a better understanding of the energy band diagram and the energy distributions of the electronic defects. A SiO2 layer was grown on wet-chemically cleaned 4H-SiC surface by wet-oxidation at 1080 ºC. The energy band alignments have been evaluated by combination of the oxide bandgap values determined from energy loss spectra of O core level photoelectron with the valence band offsets obtained from valence band spectra. Depth profile of the defect states has been investigated from changes in the PYS intensity at each step of SiO2 thinning by dipping in a dilute HF solution. The photoelectron yield from filled defect states in the energy region corresponding to the 4H-SiC bandgap was significantly increased near the SiO2/4H-SiC interface.