In this work, we report on the growth of highmobility β-Ga2O3 homoepitaxial thin films grown at a temperature much lower than the conventional growth temperature window for metalorganic vapor phase epitaxy. Low-temperature β-Ga2O3 thin films grown at 600 • C on Fe-doped (010) bulk substrates exhibits remarkable crystalline quality which is evident from the measured room temperature Hall mobility of 186 cm 2 /Vs for the unintentionally doped films. N-type doping is achieved by using Si as a dopant and a controllable doping in the range of 2×10 16 -2×10 19 cm −3 is studied. Si incorporation and activation is studied by comparing silicon concentration from secondary ion mass spectroscopy (SIMS) and electron concentration from temperature-dependent Hall measurements. The films exhibit high purity (low C and H concentrations) with very low concentration of compensating acceptors (2×10 15 cm −3 ) even at this growth temperature. Additionally, abrupt doping profile with forward decay of ∼ 5nm/dec (10 times improvement compared to what is observed for thin films grown at 810 • C) is demonstrated by growing at a lower temperature.

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β-Ga2O3 metal-semiconductor field-effect transistors are realized with superior reverse breakdown voltages (VBR) and ON currents (IDMAX). A sandwiched SiNx dielectric field-plate design is utilized that prevents etching-related damage in the active region and a deep mesa-etching was used to reduce reverse leakage. The device with LGD=34.5μm exhibits an IDMAX of 56 mA/mm, a high ION/IOFF ratio >108 and a very low reverse leakage until catastrophic breakdown at ∼4.4kV. A power figure of merit (PFOM) of 132 MW/cm2 was calculated for a VBR of ∼4.4kV. The reported results are the first >4kV-class Ga2O3 transistors to surpass the theoretical FOM of Silicon.

We report on the first demonstration of metalorganic vapor phase epitaxy-regrown (MOVPE) ohmic contacts in an all MOVPE-grown β-Ga 2 O 3 metal semiconductor field effect transistor (MESFET). The low-temperature (600 °C) heavy (n + ) Si-doped regrown layers exhibit extremely high conductivity with a sheet resistance of 73 Ω/□ and a record low metal/n + -Ga 2 O 3 contact resistance of 80 mΩ•mm and specific contact resistivity of 8.3 × 10 −7 Ω•cm 2 were achieved. The fabricated MESFETs exhibit a maximum ON current of 130 mA mm −1 and a high I ON /I OFF ratio of >10 10 . Thermal characterization was also performed to assess the device self-heating under the high current and power conditions.

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