Enhancement of channel conductivity in AlGaN/GaN heterostructure field effect transistors by AlGaN:Si back barrier

Abstract

Heterostructure field effect transistors with three AlGaN/GaN interfaces were designed and investigated. A Si-doped AlGaN back barrier was used to compensate for the reduction of channel conductivity due to a carbon doped semi-insulating GaN buffer layer. Simulation using a one dimensional Poisson-Schrödinger solver showed an enhancement of the charge carrier density which was then confirmed experimentally. Hall and magnetic field dependent mobility measurements proved the Si-doped AlGaN back barrier layer causes neither degradation of electron mobility nor a parasitic conduction channel. Id,max of the transistors was enhanced by a factor of 1.5–2 without decreasing the off-state breakdown voltage.