Positive Shifting of Vth with Enhanced DC Performance in AlGaN/GaN Schottky-Gate HEMT through Optimized UV/O3 Treated Gate Interface and Thermal Engineering

Abstract

The surface condition under the gate is critically important to improve the device characteristics and thus reliability of the AlGaN/GaN high electron mobility transistor (HEMT). In this report, we demonstrated the reduction of leakage current (IG) with betterment of current collapse in Al0.25Ga0.75N/GaN Schottky gate (SG)-HEMT by improving metal/GaN interface using optimized ultraviolet-ozone (UV/O3) plasma treatment with post metal annealing modulation at 450 °C. The x-ray photoelectron spectroscopy (XPS) was used to verify the formation of GaOXNY layer at the metal/GaN interface. Owing to, the screening of the internal/external polarization charges by 10 min. UV/O3 surface plasma treatment and incremental increase of Schottky barrier height (Φ B) with post metal annealing modulation, resulted in the positive shifting of threshold voltage (VTH) in SG-HEMT. Due to the combined effects of the UV/O3 plasma treatment and metal annealing modulation, the magnitude of the interface trap density were effectively reduced to one order of magnitude, which further improved the current collapse significantly in SG-HEMT to 2.5% from 12.2%. The 10 min. UV/O3 treated SG-HEMT with PMA modulation exhibited decent performance with an IDMAX of 620 mA mm−1, a GMMAX of 135 mS mm−1, a threshold voltage (VTH) of −1.8 V, a higher ION/IOFF ratio of approximately 1.2 × 10 9 , a subthreshold swing (SS) of 83 mV dec−1, with a low gate leakage current of 10 − 9 Amm − 1 .