Theoretical investigation of high-voltage superjunction GaN-based vertical hetero-junction field effect transistor with ununiformly doped buffer to suppress charge imbalance effect

Abstract

A superjunction GaN-based vertical heterojunction field effect transistor with ununiformly doped buffer (UDSJ-VHFET) is proposed in this paper. In contrast to the conventional superjunction vertical heterojunction field effect transistor (SJ-VHFET), the doping density of n-pillar increases linearly from top to bottom, while the p-pillar is split into three regions: linearly doped top region, uniformly doped middle region and linearly doped bottom region. The ununiform doping profile suppresses the increase of electric field peak due to the imbalanced charge and smooths the electric field distribution, thus leads to an increase of the breakdown voltage (Vbr) under charge imbalance condition. Simulation results show that with the doping dose of p-pillar 40% lower (higher) than that of the n-pillar, the Vbr and on-state resistance (Ron) of the proposed device are 6863 V and 4.25 mΩ cm2 (5751 V and 4.32 mΩ cm2), comparing with 3205 V and 4.03 mΩ cm2 (2175 V and 4.10 mΩ cm2) for the conventional SJ-VHFET. Additionally, the proposed device shows a Vbr of 12280 V and Ron of 4.29 mΩ cm2 under charge balance condition, comparing with 12874 V and 4.07 mΩ cm2 for the conventional SJ-VHFET.