Design of edge termination for GaN power Schottky diodes

The GaN Schottky diodes capable of operating in the 300-700-V range with low turn-on voltage (0.7 V) and forward conduction currents of at least 10 A at 1.4 V (with corresponding forward current density of 500 A/cm(2)) are attractive for applications ranging from power distribution in electric/hybrid electric vehicles to power management in spacecraft and geothermal, deep-well drilling telemetry. A key requirement is the need for edge-termination design to prevent premature breakdown because of field crowding at the edge of the depletion region. We describe the simulation of structures incorporating various kinds of edge termination, including dielectric overlap and ion-implanted guard rings. Dielectric overlap using 5-mu m termination of 0.1-0.2- mu m-thick SiO2 increases the breakdown voltage of quasi-vertical diodes with 3-mu m GaN epi thickness by a factor of similar to 2.7. The use of even one p-type guard ring produces about the same benefit as the optimized dielectric overlap termination.