The effect of post-metal annealing on DC and RF performance of AlGaN/GaN HEMT
The effects of gate post-metal annealing (PMA) on the DC and RF characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The unannealed and post gate-metal annealed AlGaN/GaN HEMTs were fully fabricated using NANOTAM's 0.5 μm gate length technology. PMA was performed at 450 °C for 10 min in nitrogen ambient for one of the wafers. The main focus was the effect of PMA on the electrical performance of HEMTs, including gate resistivity, transconductance, small-signal gain, output power (Pout), and threshold voltage (Vth) shift. It is achieved that HEMT with PMA has a gain of 18.5 dB, while HEMT without PMA shows a small-signal gain of 21.8 dB, as the PMA process increases the gate resistance (Rg) and decreases the transconductance (gm). The large-signal performance of the sample with PMA is better than the one without PMA, having an increase of 1.4 W/mm in Pout from 20.9 W to 24.4 W. The transistor with PMA also demonstrates a reliable gate performance and stable Vth, and the wafer exhibits better uniformity.