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Physical origin of hydrogen-adsorption-induced metallization of the SiC surface: n-type doping via formation of hydrogen bridge bond.

We perform first-principles calculations to explore the physical origin of hydrogen-induced semiconductor surface metallization observed in beta-SiC(001)-3 x 2 surface. We show that the surface metallization arises from a novel mechanism of n-type doping of surface band via formation of hydrogen bridge bonds (i.e., Si-H-Si complex). The hydrogen strengthens the weak Si-Si dimers in the subsurface by forming hydrogen bridge bonds, and donates electron to the surface conduction band.