Mar 10, 2020

Fermi-level pinning at metal/4H-SiC contact induced by SiC x O y interlayer

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 SiC x O y 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 SiC x O y layer. It was found that metal/4H-SiC contacts without a residual SiC x O y layer exhibit ideal Schottky property, while Fermi-level pinning (FLP) is caused for metal/4H-SiC contacts with a residual SiC x Oy 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 SiC x O y interlayer causes FLP, and the model was experimentally verified by intentionally forming a SiC x O y interlayer.


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