Core-level photoelectron spectroscopy study on the buffer-layer formed in approximately atmospheric pressure argon on n-type and semi-insulating SiC(0001)

Abstract

Using core-level photoelectron spectroscopy, we studied the surface of SiC(0001)-6√3 × 6√3R30° (buffer layer surface) formed on n-type and semi-insulating substrates via the approximately-atmospheric-pressure graphitization method. When the surface was exposed to air after buffer layer formation, hydrocarbons were adsorbed and oxygen atoms were chemically bonded to the carbon atoms comprising the buffer layer. Subsequently, annealing in ultra-high vacuum and an ethylene ambient allowed the removal of these oxygen atoms and hydrocarbons, and a clean buffer layer surface was obtained. Furthermore, using the peak position of Si 2p, band bending of the buffer layer on the n-type and semi-insulating substrates was estimated. A reasonable value of −0.05 eV was obtained for the n-type substrate. However, for the semi-insulating substrate, the Fermi level (Ef) was located at 0.05 eV below the conduction band minimum (CBM) on the surface. This is anomalous if we interpret the change in the CBM position over Ef from the bulk to the surface to be solely induced by band bending. To interpret this situation, we propose a mechanism in which the n-type region appears near the surface of the SiC bulk under the buffer layer.