Polarization-Assisted Acceptor Ionization in E-Mode GaN p-FET on 650-V E-mode p-GaN Gate HEMT (EPH) Platform

There is a strong motivation to develop E-mode p-channel field-effect transistor (p-FET) on the E-mode p-GaN gate HEMT (EPH) platform to enable complementary logic (CL) circuits and power integrated circuits (PICs). However, the p-FET on such platform often presents a low current density (1-5 mA/mm). A major cause is the low ionization rate of acceptors in p-GaN. This work demonstrates a polarization engineering technique that aims to enhance the ionization of acceptors in p-GaN layer. By inserting a thin AlN layer (similar to 1.5 nm) into the p-GaN, the polarization field of AlN pushes down the energy band of the lower p-GaN layer, leading to enhanced ionization of acceptors. The AlN layer also creates an energy well above AlN for holes, resulting in modulation doping effect and enhanced two-dimensional hole gas (2DHG) above AlN. The fabricated p-FET with LG = 2 mu m exhibits a n E-mode operation with V-th = -0.8 V. A low R-ON of 1.1 k ohm center dot mm is obtained. The I-ON/I-OFF is over 106. The Imax is 10.8 mA/mm, which is among the largest values in literature for E-mode GaN p-FETs on the EPH platform. Finally, an E-mode n-channel p-GaN gate HEMT is demonstrated on the same epitaxial wafer, validating the capability of the platform for CL and PICs.