CHARACTERIZATION AND ANALYSIS OF ZNO-AL DEPOSITED BY REACTIVE MAGNETRON SPUTTERING

We have deposited ZnO:Al films with state-of-the-art electro-optical p roperties by reactive magnetron sputtering from a zinc target. Films w ith resistivities of 5X10(-4) Omega cm, good optical properties over t he visible and near infrared, and with good uniformity are routinely p roduced. Resistivities down to 1.7X10(-4) Omega cm have been achieved but are accompanied by expected losses in optical properties. The fund amental mechanisms driving performance are largely determined by an in terplay between microstructure and ionized impurity scattering. At the deposition level the parameters which control these mechanisms are su bstrate bombardment and substrate temperature. At substrate temperatur es of 350 degrees C and sufficient source-to-substrate distances dopin g efficiencies approaching 100% can be achieved. At carrier concentrat ions of 4x10(20) cm(3) or higher there is a crossover from defect cont rolled transport to ionized impurity scattering dominated transport wh ich constrains improvements in conductivity. This combined with free c arrier effects on optical properties sets the limits for the electro-o ptical properties of these films. This understanding can be used to fu rther develop the deployment of these films as transparent conductors. (C) 1995 American Vacuum Society.