We report on the growth of β-Ga2O3 thin films using trimethylgallium (TMGa) as a source for gallium and pure O2 for oxidation. The growth rate of the films was found to linearly increase with the increase in the molar flow rate of TMGa and reach as high as ∼6 μm/h at a flow rate of 580 μmol/min. High purity, lightly Si-doped homoepitaxial β-Ga2O3 films with a good surface morphology, a record low temperature electron mobility exceeding 23 000 cm2/V s at 32 K, and an acceptor concentration of 2 × 1013 cm−3 were realized, showing an excellent purity film. Films with room temperature (RT) electron mobilities ranging from 71 cm2/V s to 138 cm2/V s with the corresponding free carrier densities between ∼1.1 × 1019 cm−3 and ∼1.5 × 1016 were demonstrated. For layers with the doping concentration in the range of high-1017 and low-1018 cm−3, the RT electron mobility values were consistently more than 100 cm2/V s, suggesting that TMGa is suitable to grow channel layers for lateral devices, such as field effect transistors. The results demonstrate excellent purity of the films produced and confirm the suitability of the TMGa precursor for the growth of device quality β-Ga2O3 films at a fast growth rate, meeting the demands for commercializing Ga2O3-based high voltage power devices by metalorganic chemical vapor deposition.

We report on record electron mobility values measured in lightly Si doped homoepitaxial β-Ga2O3 grown by metal-organic chemical vapor deposition. The transport properties of the films were studied using temperature-dependent Hall measurements. Numerous (010) β-Ga2O3 layers grown at different conditions showed peak electron mobility exceeding 104 cm2/V s at low temperature (LT), with the highest value of 11 704 cm2/V s at 46 K. The room temperature electron mobilities of the films were between 125 cm2/V s and 160 cm2/V s with the net background charge concentration between ∼5 × 1015 cm−3 and ∼2 × 1016 cm−3. The obtained LT mobility values for β-Ga2O3 were found to be comparable to or higher than the highest LT electron mobilities in bulk SiC and GaN films in the literature. The results demonstrate the capability of metalorganic chemical vapor deposition (MOCVD) for growing high quality ultrapure β-Ga2O3 epitaxial films that are suitable for high power electronic device applications.

We report on record low free carrier concentration values in metalorganic chemical vapor deposition (MOCVD) grown β-Ga2O3 by using N2O for oxidation. Contrary to the pure oxygen, the N2O oxidant produced β-Ga2O3 thin films co-doped with nitrogen and hydrogen, but the incorporation efficiency of both impurities is strongly dependent on key MOCVD growth parameters. An array of growth conditions resulted in β-Ga2O3 thin films with N and H concentrations ranging as high as ∼2 × 1019 cm−3 and ∼7 × 1018 cm−3, respectively, to films with no SIMS detectable N and H was identified. Films grown without detectable N and H concentrations showed a room temperature electron mobility of 153 cm2/V s with the corresponding free carrier concentration of 2.4 × 1014 cm−3. This is the lowest room temperature carrier concentration reported for MOCVD grown β-Ga2O3 with excellent electron mobility. A thin β-Ga2O3 buffer layer grown using N2O reduced the net background concentration in an oxygen grown film and is attributed to the compensation of Si at the film/substrate interface by N, which acts as a deep acceptor. The results show that the use of the N2O oxidant can lead to low background concentration and high electron mobility, which paves the road for the demonstration of high-performance power electronic devices with high breakdown voltages and low on-resistances.

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