Pulsed laser deposition of epitaxial Al-doped ZnO film on sapphire with GaN buffer layer

Al-doped ZnO (ZnO:Al) films with thickness in the range of 0.5-0.9 μm were grown epitaxially on epi-GaN/sapphire (0001) by pulsed laser deposition (PLD; XeCl, λ=308 nm). The growth parameters such as substrate temperature, oxygen pressure and pulse repetition rate were established in a sequential manner to obtain highly epitaxial ZnO:Al film. The best films were obtained at substrate temperature of 400 deg. C, oxygen pressure of 1 mTorr and pulse repetition rate of 5 Hz. Reflection high-energy electron diffraction (RHEED) and low temperature photoluminescence (PL) studies confirm the high quality epitaxial nature of the film with near match and stacking order between ZnO and GaN