Wide-range-adjusted threshold voltages for E-mode AlGaN/GaN HEMT with a p-SnO cap gate

Abstract

p-GaN cap layer has been recognized as a commercial technology to manufacture enhanced-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT); however, the difficult activation of Mg doping and etching damage of p-GaN limit the further improvement of device performance. Thus, the more cost-effective cap layer has attracted wide attention in GaN-based HEMT. In this paper, p-type tin monoxide (p-SnO) was firstly investigated as a gate cap to realize E-mode AlGaN/GaN HEMT by both Silvaco simulation and experiment. Simulation results show that by simply adjusting the thickness (50 to 200 nm) or the doping concentration (3 × 1017 to 3 × 1018 cm−3) of p-SnO, the threshold voltage (Vth) of HEMT can be continuously adjusted in the range from zero to 10 V. Simultaneously, the device demonstrated a drain current density above 120 mA mm−1, a gate breakdown voltage (VBG) of 7.5 V and a device breakdown voltage (VB) of 2470 V. What is more, the etching-free AlGaN/GaN HEMT with sputtered p-SnO gate cap were fabricated, and achieved a positive Vth of 1 V, VBG of 4.2 V and VB of 420 V, which confirms the application potential of the p-SnO film as a gate cap layer for E-mode GaN-based HEMT. This work is instructive to the design and manufacture of p-oxide gate cap E-mode AlGaN/GaN HEMT with low cost.