Growth of epitaxial ZnO thin films on lattice-matched buffer layer: Application of InGaO3(ZnO)6 single-crystalline thin film

Effects of lattice-matched substrates on growth of ZnO epitaxial films were studied. ZnO thin films were grown on single-crystalline InGaO3(ZnO)6 (IGZO) layers, which have small lattice mismatches of ∼0.8% and ∼2.2% in a- and c-axes, respectively. Epitaxial ZnO films were grown with the epitaxial relationship between the ZnO film and the single-crystalline IGZO of [0001]ZnO//[0001]IGZO//[111]YSZ and [112¯0]ZnO//[112¯0]IGZO//[11¯0]YSZ. The use of the lattice-matched substrate and optimization of film microstructure and post-annealing condition led to atomically flat surfaces at maximum process temperatures as low as 700 °C. A large Hall electron mobility ∼80 cm2 (V s)−1 (Ne: ∼2.8×1018 cm−3) was obtained even if the film thickness was only 150 nm although comparable mobilities have been reported on films having much larger thicknesses (∼1000 nm) fabricated at higher temperatures ∼1000 °C.