Quasi-normally-off GaN gate driver for high slew-rate d-mode GaN-on-Si HEMTs

This work presents a quasi-normally-off gallium nitride (GaN) transistor with positive gate threshold voltage based on depletion-mode technology, suitable for gate drivers or logic circuits. Quasi-normally-off behaviour is achieved by the series connection of multiple Schottky diodes in the source path of an initially normally-on transistor. As opposed to conventional approaches, a novel quasi-normally-off gate driver circuit avoids the static shoot-through current path in the driver final stage and ensures a safe blocking state of a d-mode power switch in case of driver failure with only one negative driver supply voltage. For evaluation a hybrid integrated GaN power module is built, comprising a 2.4 A gate driver and 600 V/ 24 A boost converter switching cell. Measurements of pulsed inductive switching up to 274 V/ 12 A show gate voltage rise and fall times of 5.4 ns and 3.8 ns, boost converter switch node transition times as low as 1.6 ns and 1.2 ns, and maximum slew-rates up to 91 V/ns during turn-on transitions, and up to 177 V/ns during turn-off transitions, respectively.