GaN-based E-mode p-FETs with polarization-doped p-type graded AlGaN channels

Abstract

Herein, a novel enhancement-mode (E-mode) GaN-based p-channel FETs (p-FETs) with a linearly graded AlGaN (LGA) p-channel is proposed and numerically studied by Silvaco TCAD. Thanks to strong polarization-induced doping, three-dimensional hole gas (3DHG) can be uniformly generated in LGA to form a continuous p-channel with a hole concentration over 1018 cm–3. Combined with an optimized recessed gate structure, the LGA p-FET can simultaneously achieve a large threshold voltage (|V TH|) > 2 V and a high current density (|J DS|) of ∼10 mA mm−1 at V DS = −10 V. Additionally, two critical parameters of the LGA p-FETs, i.e. the depth of recessed gate and initial Al composition of LGA, are specifically studied to reveal the unique carrier behavior of 3DHG in the devices. Importantly, the LGA structure is further optimized and implemented as the p-type cap layer to construct an E-mode GaN n-FET. Thereby, based on the same LGA configuration, a GaN-based inverter with the matched complementary n- and p-FETs is monolithically constructed, showing sharp voltage transition. The reported novel LGA structure and its availability in both GaN-based E-mode n- and p-FETs provides valuable insights and guidance to construct highly efficient GaN p-type devices and All-GaN-based integrated circuits for compact power electronic systems.