DC performance improvement of nanochannel AlGaN/AlN/GaN HEMTs with reduced OFF-state leakage current by post-gate annealing modulation

Abstract

In this work, the effects of a post-gate annealing (PGA) treatment on the electrical performance of AlGaN/AlN/GaN nanochannel high electron mobility transistors (NC-HEMTs) were analyzed, with various channel widths of 200, 400, 600, and 800 nm for a constant fill factor of 0.45. A systematic improvement in the DC parameters was observed in the NC-HEMTs after PGA treatment at 400 °C for 10 min. Secondary ion mass spectroscopy was performed on the 300 °C, 400 °C, and 500 °C for 10 min annealed and as-deposited NC-HEMT to optimize the PGA conditions. It was also verified that annealing at higher temperatures (>400 °C) can cause the diffusion of the gate metal (Ni/Au) into the AlGaN/AlN/GaN active layer, which subsequently degrades the device performance. The removal of shallow traps after the PGA treatment, which were created by ICP dry etching, improved the Schottky barrier height () from 0.42 eV to 1.40 eV and resulted in a significant reduction in the reverse gate leakage current (I G) of approximately more than three orders of magnitude in the NC-HEMT with a channel width of 200 nm. The reduction in the channel resistance after the PGA treatment, correspondingly improved the drift velocity, resulting in a marked improvement in the maximum transconductance (G MMAX) of 34% and considerable incremental increases in the maximum drain current (I DMAX). The NC-HEMT (W NC = 200 nm) with PGA treatment exhibited decent performance, with an I G of 9 A mm−1, an I DMAX of 470 mA mm−1, a G MMAX of 140 mS mm−1, and an ON/OFF ratio (I ON/I OFF) of approximately along with improved gate controllability, i.e. lowering of the subthreshold swing to 69 mV dec−1.