The degradation mechanism of high power S-band AlGaN/GaN HEMTs under high temperature

Abstract The radio frequency (RF) degradation mechanism under high temperature is proposed in this paper. The saturated output power ( P sat ), power added efficiency (PAE) and gain of the HEMTs deteriorate significantly under high power dissipation operation conditions, which contribute to an elevation of the junction temperature ( T j ). The high T j causes a negative shift of the threshold voltage and a reduction of electron mobility, as well as enhancing the trapping effects of the devices. As a result, the P sat and PAE of the high-power HEMTs ( P sat = 152 W) decreased by 0.76 dB and 8.3%, respectively, which is more severe compared to low-power HEMTs ( P sat = 20 W), where P sat and PAE reduced by 0.16 dB and 3.1% when the operation temperature was increased from 25 °C to 150 °C. By increasing the gate-to-drain distance from 1.625 to 2.175 μ m, drain current stability and high temperature reverse bias reliability are improved. The results demonstrate that the trapping effect can be suppressed by decreasing the electric field under the gate; therefore, the RF output characteristics are boosted by 1.2 W, 1 dB and 2.6% for a device with gate width of 11.52 mm.