Post-annealing effects on device performance of AlGaN/GaN HFETs

Abstract

The effects of post-annealing on DC, RF, and power performances of AlGaN/GaN HEMTs with a gate-length of 0.3 μm were investigated. The results show that the post-annealing technique can improve the device breakdown voltage and device uniformity, reduce the trapping centers on AlGaN surface and/or GaN buffer layer after the post-annealing, and adjust the device threshold voltage. Specifically, after 20-min post-annealing at 400 °C, the gate-to-drain breakdown voltage of the device exhibits remarkable improvement from 10 to 187 V. The maximum extrinsic transconductance ( g m) increases from 238 to 254 mS/mm at a drain bias of 10 V after 10-min annealing at 400 °C. The threshold voltage shifts from −3.3 to −2.7 V. However, due to the decrease of two-dimensional electron gas concentration, the maximum drain current at a gate bias of 1 V reduces slightly from 918 to 904 mA/mm. The values of the unity current gain cut-off frequency ( f T) and the maximum oscillation frequency ( f MAX) increase after annealing. The output power and gain at 10 GHz were improved from 16.4 dBm and 11.4 dB to 22.4 dBm and 17.9 dB, respectively.