Si content variation and influence of deposition atmosphere in homoepitaxial Si-doped β-Ga2O3 films by pulsed laser deposition

Carrier concentration control by impurity dopants in epitaxial Ga2O3 thin films is progressing to deliver high mobility films for device structures. Si-doped Ga2O3 thin films were fabricated by pulsed laser deposition on (010) beta-Ga2O3 substrates from Ga2O3 targets with 0.01-1 wt.% SiO2 yielding films with an electron mobility range consistent with other vapor growth techniques. Single crystal, homoepitaxial growth as determined by high resolution transmission electron microscopy and x-ray diffraction was observed, with a high Si dopant level causing film tensile strain as indicated by both techniques. The influence of oxygen on conductivity using different O-2 pressures during deposition and O-2/Ar mixtures with a fixed working pressure of 1.33 Pa was determined. With this optimized deposition pressure and atmosphere condition, a carrier concentration and mobility range of 3.25 x 10(19) cm(-3) -1.75 x 10(20) cm(-3) and 20 cm(2)/V s-27 cm(2)/V s was achieved in films from Ga2O3-0.025 wt.% SiO2 and Ga2O3-1 wt.% SiO2 targets, respectively. A highest conductivity of 798 S cm(-1) was achieved in films deposited at 550 degrees C-590 degrees C with targets of 0.05-1 wt.% SiO2. The electrically active and chemical Si content in films deposited at 550 degrees C was found to exceed the expected Si ablation target composition in all cases except the highest 1 wt.% SiO2 target attributed to imprecise target manufacturer compositional control at low SiO2 doping levels. Diminished electrical and structural quality films resulted from all targets at a 450 degrees C deposition temperature. (C) 2018 Author(s).