Design and implementation of floating field ring edge termination on vertical geometry β-Ga2O3 rectifiers

One of the key areas for implementation of high-power Ga2O3 rectifiers is the mitigation of electric field crowding at the edge of the depletion region to avoid premature breakdown. Floating metal field rings (FMRs) are a relatively simple approach for achieving this. We report simulations of the spacing (1–10 μm), width (2–15 μm), number of rings, and also the effect of biasing the rings (0–280 V) and including a field plate at the periphery of the rings on the breakdown voltage of a vertical geometry rectifier with a range of doping concentrations (5 × 1015–4 × 1016 cm−3) in the drift region. Improvements in breakdown voltage of 19%–54% relative to an unterminated rectifier are found with an optimum design of the field rings. The experimental results on rectifiers with different FMR geometries show an RON of 4.5–4.9 mΩ cm2, a turn-on voltage of 0.96–0.94 V, a high on-off ratio of >5 × 106, an ideality factor of 1.03, and a Schottky barrier height of 1.03 eV at room temperature. These devices have similar forward electrical characteristics, indicating that FMRs do not degrade the device rectifying performance.