Performance Enhancement of AlGaN/GaN HEMT via Trap-State Improvement Using O₂ Plasma Treatment

Herein, we present a detailed analysis of the effects of O-2 plasma treatment on the AlGaN barrier volume trap states in an Al0.45Ga0.55N/GaN high-electron mobility transistor. Compared to that of the as-grown sample, the single short-pulse I-D-V(GS )characterization of the plasma-treated sample exhibited lower charge trapping inside the AlGaN barrier. The 1/f low-frequency noise characterization revealed a significant reduction of approximately 67% in the volume trap density of the AlGaN barrier layer after O-2 plasma treatment. This was achieved by the formation of Al-O and Ga-O bonds via the penetration of oxygen ions into the AlGaN bulk, which resulted in reduced trap state density in the AlGaN barrier. In addition, the Schot-tky characteristics were improved notably. Consequently, the O-2 plasma-treated sample did not display current collapse and showed steady drain current output under the reverse-sweep drain-stress bias conditions. Further-more, the plasma treatment significantly reduced the RF transconductance (g(m)) collapse in the as-grown sample, and significantly increased the f(T)/f(max) of the plasma-treated sample from 65/70 to 120/230 GHz for L-g = 80 nm devices, respectively. Last, the O-2 plasma-treated sample showed substantial improvements in P-out_max, power added effi-ciency (PAE), and linear gain from 1.25 W/mm, 20%, and 15 dB to 2.4 W/mm, 50%, and 19 dB, respectively.