Enhancement mode β-(Al0.19Ga0.81)2O3/Ga2O3 HFETs with superlattice back-barrier layer

Abstract

In this study, we numerically investigate the improvement in maximum drain current of an enhancement-mode β-(Al0.19Ga0.81)2O3/Ga2O3 heterostructure field-effect transistor (HFET) that employs a superlattice back-barrier layer. The measured transfer characteristics of a recently reported enhancement-mode β-(Al0.19Ga0.81)2O3/Ga2O3 HFET are reproduced using a device simulation and modeling tool. Subsequently, the transfer, output, radio frequency (RF), and off-state breakdown characteristics of the proposed device are revealed. The calculated off-state breakdown voltage is drastically enhanced from 26 V to 93 V for a gate length (LG) of 195 nm and a gate-to-drain separation (LGD) of 190 nm because of the superlattice back-barrier, which is one of the highest breakdown voltages reported for submicron Beta-Gallium Oxide (β-Ga2O3) transistors. Moreover, the insertion of the superlattice back-barrier layer improves subthreshold characteristics, resulting in a positive shift in the threshold voltage. The results indicate that using the superlattice back-barrier can dramatically enhance both the off-state current characteristics and RF characteristics of the enhancement mode in highly scaled β-Ga2O3 HFETs.