ESTIMATION AND VERIFICATION OF THE ELECTRICAL-PROPERTIES OF INDIUM TIN OXIDE-BASED ON THE ENERGY-BAND DIAGRAM

Indium tin oxide (ITO) is a transparent conducting oxide used in a var iety of optoelectronic applications. In order to optimize the electric al conductivity of ITO thin films it is necessary to determine this pr operty as a function of optimum electron concentration (e.g., doping o f In2O3 with Sn). A new software program called CRYSTAL 92 is used to determine the energy band diagrams of In2O3 and In2O3 doped with Sn. U sing the curvature of the conduction bands, the effective mass of the electrons is estimated and an empirical relationship is established be tween the effective mass and free carrier concentration using experime ntally observed optical effective mass values. The importance of the v arying electron effective mass in the prediction of the electron mobil ity? and hence the electrical conductivity, is shown here by comparing the published experimental results with the estimated results. The li miting factor in thr electron mobility appears to be either grain boun dary scattering or ion impurity scattering. The mobility due to neutra l impurity scattering appears to have a negligible effect on the overa ll mobility unless the neutral impurity concentration reaches extremel y high values. (C) 1996 American Vacuum Society.