Optical and electrical properties of ZnO:Al thin films synthesized by low-pressure pulsed laser deposition

ZnO:Al thin films were prepared at a low oxygen pressure between 0.02 and 0.1 Pa by pulsed laser deposition (PLD). The structure as well as their optical and electrical properties was investigated by X-ray diffraction, optical transmittance spectroscopy, and Hall measurements. The ZnO:Al films possess resistivity of the order of 10−4 Ω cm and the optical transmittance exceeds 80% in the visible range. The highest electron concentration (1.18×1021 cm−3) is achieved at a deposition pressure of 0.02 Pa and it decreases slightly with increasing oxygen pressure. The band gap is found to depend on the electron concentration.