Resonant photoemission at the oxygen K edge as a tool to study the electronic properties of defects at SiO2 /Si and SiO2 /SiC interfaces

Silicon is by far the most important material used in microelectronics, partly due to the excellent electronic properties of its native oxide (SiO₂), but substitute semiconductors are constantly the matter of research. SiC is one of the most promising candidates, also because of the formation of SiO₂ as native oxide. However, the SiO₂/SiC interface has very poor electrical properties due to a very high density of interface states which reduce its functionality in MIS devices. We have studied the electronic properties of defects in the SiO₂/Si and SiO₂/SiC interfaces by means of XAS, XPS and resonant photoemission at the O 1s and the Si 2p edges, using silicon dioxide thermally grown with thicknesses below 10 nm. Our XAS data are in perfect agreement with literature; in addition, resonant photoemission reveals the resonant contributions of the individual valence states. For the main peaks in the valence band we find accordance between the resonant behaviour and the absorption spectra, except for the peaks at −15 eV binding energy, whose resonant photoemission spectra have extra features. One of them is present in both interfaces and is due to similar defects, while another one at lower photon energy is present only for the SiO₂/SiC interface. This is related to a defect state which is not present at the SiO₂/Si interface.