Electrical transport properties of single undoped and n-type doped InN nanowires

Electrical transport properties of undoped and n-type doped InN nanowires grown by molecular beam epitaxy were studied by current-voltage and back-gate field-effect transistor measurements. The current-voltage characteristics show ohmic behavior in the temperature range between 4 and 300 K. Down to about 120 K a linear decrease in resistance with temperature is observed. The investigation of a large number of nanowires revealed for undoped as well as doped wires an approximately linear relation between the normalized conductance and diameter for wires with a diameter below 100 nm. This shows that the main conduction takes place in the tubular surface accumulation layer of the wires. In contrast, for doped wires with a diameter larger than 100 nm a quadratic dependence of conduction on the diameter was found, which is attributed to bulk conductance as the main contribution. The successful doping of the wires is confirmed by an enhanced conduction and by the results of the back-gate field-effect transistor measurements.