The impact of post gate annealing on microwave noise performance of AlGaN/GaN HEMTs

The effects of post gate annealing on microwave noise performance of AlGaN/GaN HEMTs on SiC substrate were investigated. The results show that post Schottky gate annealing under an optimized condition, 400 °C for 10 min in N2 ambient, can increase the current driving capability, reduce gate leakage current, and improve the microwave noise performance. Specifically, the maximum extrinsic transconductance increased from 223 mS/mm to 233 mS/mm. The 1 mA/mm gate leakage current at Vgs = − 30 V reduced to 4 nA/mm. Before annealing, the device exhibited a minimum noise figure of 0.99 dB at 4 GHz. It decreased to 0.63 dB and the associated gain increased from 13.2 dB to 17.4 dB at the mean time. The change is even more significant under high current operation. At 4 GHz, the 4.90 dB NFmin at Ids of 670 mA/mm decreased more than 3 dB to 1.12 dB. Based on a simple noise model, the improvement of the microwave noise performance is attributed to the significant decrease of the gate leakage current.