Effect of front and back gates on β-Ga₂O₃ nano-belt field-effect transistors

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 × 10⁻³mA 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.