This study demonstrated the exfoliation of a two-dimensional (2D) β-Ga2O3 nano-belt and subsequent processing into a thin film transistor structure. This mechanical exfoliation and transfer method produces β-Ga2O3 nano-belts with a pristine surface as well as a continuous defect-free interface with the SiO2/Si substrate. This β-Ga2O3 nano-belt based transistor displayed an on/off ratio that increased from approximately 10(4) to 10(7) over the operating temperature range of 20 °C to 250 °C. No electrical breakdown was observed in our measurements up to VDS = +40 V and VGS = -60 V between 25 °C and 250 °C. Additionally, the electrical characteristics were not degraded after a month-long storage in ambient air. The demonstration of high-temperature/high-voltage operation of quasi-2D β-Ga2O3 nano-belts contrasts with traditional 2D materials such as transition metal dichalcogenides that intrinsically have limited temperature and power operational envelopes owing to their narrow bandgap. This work motivates the application of 2D β-Ga2O3 to high power nano-electronic devices for harsh environments such as high temperature chemical sensors and photodetectors as well as the miniaturization of power circuits and cooling systems in nano-electronics.

We fabricated solar-blind photodetectors based on exfoliated two-dimensional β-Ga2O3 flakes, and then systematically characterized their photoresponsive properties. They exhibit extraordinary photoresponsive properties including the highest responsivity among reported semiconductor thin-film solar-blind photodetectors.

Layered materials separated from each bulk crystal can be assembled to form a strain-free heterostructure by using the van der Waals interaction. We demonstrated a heterostructure n-channel depletion-mode β-GaO junction field-effect transistor (JFET) through van der Waals bonding with an exfoliated p-WSe flake. Typical diode characteristics with a high rectifying ratio of ∼10 were observed in a p-WSe/n-GaO heterostructure diode, where WSe and β-GaO were obtained by mechanically exfoliating each crystal. Layered JFETs exhibited an excellent I- V output as well as I- V transfer characteristics with a high on/off ratio (∼10) and low subthreshold swing (133 mV/dec). Saturated output currents were observed with a threshold voltage of -5.1 V and a three-terminal breakdown voltage of +144 V. Electrical performances of the fabricated heterostructure JFET were maintained at elevated temperatures with outstanding air stability. Our WSe-GaO heterostructure JFET paves the way to the low-dimensional high-power devices, enabling miniaturization of the integrated power electronic systems.

Field effect transistors (FETs) using SiO2 and Al2O3 as the gate oxides for the back and front sides, respectively, were fabricated on exfoliated two-dimensional (2D) β-Ga2O3 nano-belts transferred to a SiO2/Si substrate. The mechanical exfoliation and transfer process produced nano-belts with smooth surface morphologies and a uniform low defect density interface with the SiO2/Si substrate. The depletion mode nanobelt transistors exhibited better channel modulation with both front and back gates operational compared to either front or back-gating alone. The maximum transconductance was ∼4.4 mS mm−1 with front and back-gating and ∼3.7 mS mm−1 with front-gating only and a maximum drain source current density of 60 mA mm−1 was achieved at a drain-source voltage of 10 V. The FETs had on/off ratios of ∼105 at 25 °C with gate-source current densities of ∼2 × 10−3 mA mm−1 at a gate voltage of −30 V. The device characteristics were stable over more than a month for storage in air ambient and the results show the potential of 2D β-Ga2O3 for power nanoelectronics.