Multi-Fin <i>β</i> -Ga ₂ O ₃ Vertical FinFET With Interfin Field Oxide Exhibiting a Breakdown Voltage of 1.8 kV and Power Figure of Merit of 1 GW/cm ²

We present a multi-fin, normally-off vertical FinFET based on β-Ga2O3, incorporating an inter-fin field oxide layer to enhance the breakdown voltage. Narrow fins with a width of 200 nm were fabricated using electron beam lithography, enabling enhancement-mode operation with a positive threshold voltage of 1.8 V. A thick dielectric layer was deposited at the bottom of the inter-fin trenches, serving as a field oxide, which increased the breakdown voltage to 1.8 kV—more than double the 800 V observed in devices without the field oxide. The device demonstrates a specific on-resistance of 3.2 mΩ-cm2and supports a maximum current density of 1.2 kA/cm2. These characteristics yield a record-high power figure of merit of 1.01 GW/cm2for any multi-fin β-Ga2O3-based vertical transistor.