Field-plated β-Ga ₂ O ₃ nanoFETs with a breakdown voltage of over 300 V pave a way for downsizing power electronic devices.

The nature of ultra-wide energy bandgap (UWBG) semiconductors enables transistors to withstand large voltage swings, ensuring stable high-power and high-efficiency operation. The potential of UWBG β-Ga₂O₃ nano-field effect transistors (nano-FETs) has not been fully explored due to premature avalanche breakdown in these devices, despite their extremely high critical breakdown field. An exfoliated β-Ga₂O₃ nano-layer was fabricated into a depletion-mode nano-FET integrated with dual field-modulating layers to redistribute the electric field crowded around the drain edge of the gate electrode. A stepped-gate field-plate and a source-grounded field-modulating electrode were integrated into the planar β-Ga₂O₃ nano-FETs. Excellent output and transfer characteristics were demonstrated, i.e. a low subthreshold swing (95.0 mV dec⁻¹) and high on/off ratio (∼10¹⁰), achieving an ultra-high off-state three-terminal breakdown voltage of 412 V. The experimental results were compared with numerical simulations, confirming the efficacy of the dual-field plate structure. The introduction of multiple field-modulating plates into the UWBG β-Ga₂O₃ nano-FETs greatly increased the voltage swings to over 400 V, suggesting the possibility for small footprint power electronics.

4H-SiC lateral double implanted metal-oxide-semiconductor field effect transistors (LDIMOSFET) were fabricated on on-axis semi-insulating SiC substrates without using an epi-layer. The LDIMOSFET adopted a current path layer (CPL), which was formed by ion-implantation. The CPL works as a drift region between gate and drain. By using on-axis semi-insulating substrate and optimized CPL parameters, breakdown voltage (BV) of 1093 V and specific on-resistance (R on,sp) of 89.8 mΩ&cm 2 were obtained in devices with 20 µm long CPL. Experimentally extracted field-effect channel mobility was 21.7 cm 2 &V %1 &s %1 and the figure-of-merit (BV 2 /R on,sp) was 13.3 MW/cm 2 .

The three-terminal off-state breakdown voltage of the β-Ga₂O₃ nanoFET with beveled field-plate (FP) was obtained at +441 V, enhanced by downstream plasma-etched 60° h-BN FP structure.