Photoemission of the SiO2–SiC heterointerface

Abstract

Photoelectron spectroscopy has been performed on SiC surfaces to investigate the valence band characteristics during SiO2 formation. Various stages of the oxide development were investigated. The √3×√3R30° surface is used as the initial surface for the oxidation experiments. The substrates were exposed to a succession of a 30 s oxygen exposure, two 30 s oxygen plasmas, and finally, a plasma-enhanced chemical vapor deposition SiO2 deposition. Ultraviolet photoemission spectroscopy was employed to measure the valence band discontinuity for the oxide on n-type 6H and n-type 4H SiC substrates for each step in the oxidation process. X-ray photoemission spectroscopy was used to confirm the valence band offset. The valence band discontinuity was determined to be 2.0 eV. Furthermore, the location of the valence band maximum of the SiC to the conduction band minimum of the SiO2 is determined to be a constant (∼7.0 eV) between 6H and 4H SiC. Band bending effects are directly measured from ultraviolet photoemission spectroscopy (UPS) and x-ray photoemission spectroscopy. From the UPS measurements of the band bending effects, the interface state density is determined to be ∼5×1012 cm−2.