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

Abstract The RF degradation mechanism under high temperature of high power GaN-based high electron mobility transistors (HEMTs) are proposed in this paper. The saturated output power (Psat), power added efficiency (PAE) and gain of the HEMTs deteriorated obviously under large power dissipation operation conditions which contribute to the elevate of junction temperature (Tj). The high Tj caused the negative shift of threshold voltage and the reduction of electron mobility, meanwhile, promoting trapping effects of the devices. As a result, the Psat and PAE of high power HEMTs (Psat = 152 W) decreased 0.76 dB and 8.3% which is more serious than low power HEMTs (Psat = 20 W) with Psat and PAE reducing 0.16 dB and 3.1% as elevating the operation temperature from 25 to 150 oC. By increasing the gate-to-drain distance from 1.625 to 2.175 μm, the stability of drain current and HTRB reliability are improved. It demonstrates 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 the device with gate width of 11.52 mm.