Heteroepitaxial Growth Of Ga2o3 Thin Films Of Various Phase Composition By Oxidation Of Ga In Hydrogen-Oxygen Plasmas

We describe a novel plasma-chemical method for Ga2O3 thin films synthesis, in which high-purity elemental Ga is delivered by hydrogen flow into the plasma discharge zone to react with O-2. Radio Frequency (40 MHz) non-equilibrium low temperature plasma discharge at low pressure (0.01 Torr) is applied for initiation of interaction between these precursors. Optical Emission Spectroscopy together with quantum-chemical calculations was used to determine the main reaction pathways and reacting species appearing in the plasma discharge. For a low growth temperature of 350 degrees C and high plasma power of 50 W, the Ga2O3 films deposited on basal plane sapphire are textured beta-Ga2O3 with (-201) orientation. At low plasma power of 30 W and low growth temperature of 350 degrees C, the layers are dominated by the polycrystalline epsilon(k) phase. Increasing the growth temperature under these low plasma power conditions from 350 degrees C to 550 degrees C leads to the grains ripening and the conversion of the films into the polycrystalline beta-polytype. Electrical measurements on the films grown under high power conditions on sapphire showed them to be semi-insulating, with the Fermi level pinned near E-c-0.7 eV. Films on Si substrates had low donor concentrations of similar to 10(15) cm(-3), most likely due to Si autodoping from the Si substrate.