Analytical model and simulation study of a novel enhancement-mode Ga2O3 MISFET realized by p-GaN gate

Abstract

Abstract In this paper, we propose a novel junction-less Ga2O3 metal–insulator–semiconductor field effect transistor (MISFET) with a p-GaN gate, named p-GaN Ga2O3-MISFET. A heavily doped thin layer p-GaN is set in the trench gate region to deeply deplete the n-Ga2O3 channel region owing to the high work function of the p-GaN. Thus, a high threshold voltage (V TH) and breakdown voltage (BV) can be obtained even with a wide-fin design and low interface charge density (n int), which ensures easy fabrication and a stable V TH. Analytical modeling and experimentally calibrated technology computer aided design (TCAD) simulations confirm that with the increase of fin width (W Fin) from 0.1 μm to 0.5 μm, the V TH of the p-GaN Ga2O3-MISFET varies from 3.2 V to 2.4 V with n int = −1 × 1011 cm−2, which is always about 2.2 V higher than those of conventional junction-less Ga2O3 MISFETs (CJL-MISFET). In addition, the BV of the CJL-MISFET decreases from ∼3400 V to ∼45 V with increasing W Fin due to soft breakdown, while the BV of the p-GaN MISFET only decreases to 2800 V due to the enhanced electric field at the corner of the trench gate. Moreover, the activation energy and doping concentration (when larger than 3 × 1019 cm−3) of p-GaN barely affect the V TH. Even so, a high V TH remained in a common range of interface charge (from 1 × 1013 cm−2 to 2 × 1013 cm−2) at the p-GaN/Al2O3 interface.