Impact of Multi-Layer Carbon-Doped/Undoped GaN Buffer on Suppression of Current Collapse in AlGaN/GaN HFETs

Abstract

We present a new semi-insulating GaN buffer layer, which consists of multiple carbon-doped and undoped GaN layers, suitable for AlGaN / AlN / GaN heterojunction field effect transistors. The proposed buffer structure was designed to minimize the total carbon incorporation into the buffer layer because carbon atoms in GaN are a possible cause of deterioration in structural quality and device characteristics such as current collapse. With this new buffer structure, current collapse in GaN MISHFET is drastically reduced while maintaining high breakdown characteristics. We argue that electron transfer from the undoped GaN to the carbon-doped GaN layer leads to total depletion of the undoped GaN layer and effectively compensates the deep-acceptor states in the carbon-doped GaN layer. This mechanism results in high-insulating buffer characteristic and opens the avenue for current collapse suppression in AlGaN / AlN / GaN MISHFET.