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

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 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 (ΦB) 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, a GMMAX of 135 mS/mm, a VTH of −1.8 V, a higher ION/IOFF ratio of approximately 1.2×10^9, a subthreshold swing (SS) of 83 mV/dec, with a low gate leakage current of〖10〗^(-9) A/mm.

Remarkable Reduction in IG with an Explicit Investigation of the Leakage Conduction Mechanisms in a Dual Surface-Modified Al2O3/SiO2 Stack Layer AlGaN/GaN MOS-HEMT

“…The comparatively higher (f max × L G ) was recorded in the MOS-HEMT after PGA modification in contrast with previous reports as indicated in Table 1. The interface state density (D it ) for the dual surface-treated MOS-HEMT can be extracted from a previously reported formula [47] to be 1.61 × 10 12 eV −1 cm −2 , which is significantly improved from that of the conventional HEMT 1.1 × 10 13 eV −1 cm −2 . For the SiO 2 MOS-HEMT, D it was 3.8 × 10 12 eV −1 cm −2 .…”