Bipolarity in electrical conduction of transparent oxide semiconductor CuInO2 with delafossite structure

A transparent oxide semiconductor with delafossite structure, CuInO2, was found to exhibit both p-type and n-type conduction by doping of an appropriate impurity and tuning of proper film-deposition conditions. Thin films of Ca-doped or Sn-doped CuInO2 (optical band gap = similar to3.9 eV) were prepared on alpha -Al2O3(001) single crystal substrates by pulsed laser deposition method. The films were deposited at 723 K in O-2 atmosphere of 1.0 Pa for the Ca-doped films or 1.5 Pa for the Sn-doped films. The positive sign of the Seebeck coefficient demonstrated p-type conduction in the Ca-doped films, while the Seebeck coefficient of the Sn-doped films was negative indicating n-type conductivity. The electrical conductivities of Ca-doped and Sn-doped CuInO2 thin films were 2.8 x 10(-3) S cm(-1) and 3.8 x 10(-3) S cm(-1), respectively, at 300 K. (C) 2001 American Institute of Physics.