Al-impurity-doped transparent conductive oxide films of In2O3-ZnO system

The effects of Al2O3 dopings in pseudobinary (In2O3)(1-delta)(2ZnO)(delta) films were investigated, and carrier generation mechanism was discussed. Here the 6 value is the ratio of Zn/(Zn + In). For Al2O3 doping below 2 wt%, low-resitivity amorphous films in 2-4 x 10(-4) Q CM were deposited over a narrow range of delta=Zn/(Zn+In) (0.2less than or equal todeltaless than or equal to0.4). At Al2O3 2 wt% doping, the resistivity was improved in the same narrow range of delta. Using a ZnO:Al target with 3 wt% Al2O3, film resistivities of 2-4 x 10(-4) Omega CM were attained over a relatively wide range of 6 in the amorphous phase (0.2less than or equal todeltaless than or equal to0.6). This result was due to the increase in carrier concentration at delta = 0.3-0.6. The Al2O3 doping also influenced on optical band gap: band gap shrinkage for Al2O3 = 2 wt% and band gap widening for Al2O3 = 3 wt%. For homologous crystalline films, Al2O3 doping decreased carrier concentration, independent of the level of Al2O3 doping. The Al2O3 doping increased linearly optical band gap energy. These results indicate that the Al atoms are impurities that distort the lattice in homologous film. (C) 2004 Published by Elsevier Ltd.