Novel high-voltage GaN CAVET with high threshold voltage and low reverse conduction loss

Abstract

A novel GaN current-aperture vertical electron transistor (CAVET) with an energy band pinning (EBP) structure (EBP-CAVET) is proposed and investigated by simulations. The EBP-CAVET is featured with hybrid contacts on the p-GaN layer, locally having Ohmic contact combined with Schottky gate metals in the longitudinal direction. The Ohmic contact is shorted to the source electrode and the Schottky gate metals are shorted to the gate electrode. The conduction band (Ec) in the gate region is modulated by the alternately arranged contacts. In the Ohmic contact region, Ec remains a fixed value, which acts as an energy band pinning and suppresses the variation of the Ec in the gate region. In the on-state (VGS > 0 V) and blocking-state with high VDS, the EBP structure inhibits the Ec shifting downwards in the gate region to achieve a high threshold voltage (Vth), a low leakage current density (Jdss), and a high breakdown voltage (BV). In the reverse conduction state (VDS < 0 V &VGS ≤ 0 V), the EBP structure suppresses the Ec shifting upwards to achieve a low and independent of gate bias reverse turn-on voltage (VRT). The proposed EBP-CAVET achieves a high Vth of 2.10 V, a VRT of 0.69 V, a low Jdss of 3.1 × 10−11 A/cm2 at VDS = 1000 V, a high BV of 1660 V. Compared with an integrated Schottky barrier diode or fin diode in a field effect transistor (FET), the EBP structure occupies a much smaller chip area. Thus, the EBP-CAVET achieves a low specific ON-resistance (Ron,sp) of 1.19 mΩ cm2 and an extremely high power-figure-of-merit (PFOM) up to 2.32 GW/cm2. Consequently, the proposed structure presents a new design concept and enhances the application potential for GaN CAVET with high Vth and low reverse conduction loss.