Normally-Off GaN Transistors for Power Switching Applications

Abstract

Normally-off high voltage GaN-HFETs for switching applications are presented. Normally-off operation with threshold voltages of more than 1 V and 6 V gate swing has been obtained by using p-type GaN as gate. Different (Al)GaN-based buffer compositions using intentional doping and potential barriers have been used to obtain high blocking voltages. 1000 V blocking was obtained for devices with carbon-doped buffer structures, however, they suffer from a stronger increased dynamic on-state resistance as compared to devices based on an iron-doped GaN-buffer or an AlGaN-buffer. The best trade-off between low dispersion and high blocking strength was obtained for a modified carbon-doped GaN-buffer that showed only a 2.6x increase of the dynamic on-state resistance for 500 V switching.