In this work, we report record electron mobility values in unintentionally doped β-Ga₂O₃ films grown by metal-organic chemical vapor deposition. Using degenerately Sn-doped regrown n+ β-Ga₂O₃ contact layers, we were able to maintain Ohmic contact to the β-Ga₂O₃ films down to 40 K, allowing for reliable temperature-dependent Hall measurement. An electron mobility of 176 cm²/V s and 3481 cm²/V s were measured at room temperature and 54 K, respectively. The room and low temperature mobilities are both among the highest reported values in a bulk β-Ga₂O₃ film. A low net background charge concentration of 7.4 × 10¹⁵ cm⁻³ was confirmed by both temperature dependent Hall measurement and capacitance-voltage measurement. The feasibility of achieving low background impurity concentration and high electron mobility paves the road for the demonstration of high performance power electronics with high breakdown voltages and low on-resistances.

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 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.

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 demonstrate over 3 kV gate-pad-connected field plated (GPFP) β-Ga2O3 lateral MESFETs with high lateral figure of merit (LFOM) using metalorganic vapor phase epitaxy (MOVPE) grown channel layers and regrown ohmic contact layers. Using an improved low-temperature MOVPE selective area epitaxy process, we show that a total contact resistance to the channel as low as 1.4 Ω.mm can be achieved. The GPFP design adopted here using plasma-enhanced chemical vapor deposition (PECVD) deposited SiNx dielectric and SiNX/SiO2 wrap-around passivation exhibits up to ~14% improved RON, up to ~70% improved breakdown voltage (VBR = VDS-VGS) resulting in up to 3× higher LFOM compared to non-FP β-Ga2O3 lateral MESFETs. The VBR (~2.5 kV) and LFOM (355 MW/cm2) measured simultaneously in our GPFP β-Ga2O3 lateral MESFET (with LGD = 10μm) is the highest value achieved in any depletion-mode β-Ga2O3 lateral device to date.