Electrical Conductivity of InN Nanowires and the Influence of the Native Indium Oxide Formed at Their Surface

The electrical properties of InN nanowires were investigated in four-point probe measurements. The dependence of the conductance on the wire diameter allows distinguishing between core bulk (quadratic) and shell sheet (linear) contributions. Evidence of the formation of a thin In2O3 layer at the surface of the nanowires is provided by X-ray core level photoemission spectroscopy. The shell conductivity is therefore ascribed to an electron accumulation layer forming at the radial InN/In2O3 interface. Although conductance through the accumulation layer dominates for nanowires below a critical diameter of about 55 nm, the core channel cannot be neglected, even for small nanowires.