Dependence of the resistivity and the transmittance of sputterdeposited Ga-doped ZnO films on oxygen partial pressure and sputtering temperature

Ga-doped ZnO (GZO) thin films were prepared by rf magnetron sputtering and dependence of the electrical resistivity and the transmittance of the GZO films on the oxygen partial pressure (R = the O2/ Ar gas flow ratio) and the substrate temperature were investigated. The resistivity of the GZO film decreases first and then increases with an increase in the substrate temperature (T). Aminimum resistivity obtained with a substrate temperature of 300 C is 3.3 · 10–4 Wcm. The resistivity nearly does not change with R for R < 0.25. The decrease in the resistivity for R < 0.25 is attributed to enhancement in crystallinity, whereas the increase in the resistivity for R > 0.25 to precipitation of gallium oxides at grain boundaries. Optical transmittance of the GZO films is enhanced by increasing R up to 0.75. This enhancement in the transmittance is due to a decrease in oxygen vacancy concentration and a decrease in surface roughness with R.