Effect of high substrate temperature on Al-doped ZnO thin films grown by pulsed laser deposition

Thin films of Al-doped ZnO were grown on Al2O3 at high substrate temperature of 750 °C by pulsed laser deposition technique with different Al concentrations. Highly c-axis oriented and transparent (80%) thin films were obtained at 1 mTorr of O2 pressure. Increase of Al doping changes the stress in the ZnO films from tensile to compressive as measured from c-parameter. The XPS spectra indicated that the presence of hydroxides in the thin films. The surface morphology shows the decrease in surface roughness with Al doping. The maximum carrier concentration was found to be 4×1019 cm−3 with a mobility of 49 cm2 V−1 s−1 for 1% Al doping. However, the resistivity increased with increase in Al concentration. The bandgap was observed to increase with increase of Al doping and this may be attributed to Burstein–Moss shift and the stress in the films.