Tunable n-type conductivity and transport properties of Ga-doped ZnO nanowire arrays

A controlled growth and doping process of well-aligned Ga-doped ZnO nanowire (NW) arrays through thermal evaporation was reported to determine the tunable n-type conductivity and transport properties of the NWs. The results show that the NWs have a uniform diameter of 60-80 nm and the wire length can be controlled by varying the growth time. The growth dierction of ZnO nanowires can be systematically varied through dopant content while the growth is dictated by the formation of the lowest-free-energy surface in NWs. A small red shift in UV emission is observed in Ga-doped ZnO nanotips and thin films and the apparent band gap narrowing related to Ga doping in ZnO is attributed to semiconductor-to-metal transition.