Fermi-level pinning at metal/4H-SiC contact induced by SiCxOy interlayer

Abstract

We investigated the impact of defects formed at the SiO2/4H-SiC interface on the Schottky barrier height of metal/4H-SiC(0001) contacts. We found that an ultra-thin SiCxOy layer remains on the 4H-SiC surface after SiO2 sputtering at various powers and its removal by diluted hydro fluoride solution. Ni, Mo, or Al was deposited on 4H-SiC surface without and with a residual SiCxOy layer. It was found that metal/4H-SiC contacts without a residual SiCxOy layer exhibit ideal Schottky property, while Fermi-level pinning (FLP) is caused for metal/4H-SiC contacts with a residual SiCxOy layer, and the degree of FLP increases increasing sputtering power of SiO2. The pinning position was estimated to be ∼0.8 eV below the conduction band minimum of 4H-SiC, which does not correspond to the charge neutrality level of 4H-SiC. Finally, we proposed a physical model where a SiCxOy interlayer causes FLP, and the model was experimentally verified by intentionally forming a SiCxOy interlayer.