High Power-Added-Efficiency AlGaN/GaN E-Mode HEMTs for Low-Supply-Voltage RF Terminal Applications

Abstract—In this paper, an enhancement-mode (E-mode) GaN high electron mobility transistors (HEMTs) with an innovational inverted trapezoidal recessed-gate is successfully fabricated using a developed variable pressure gate etching process, which contributes to a 0.41 V positive threshold voltage (VTH). Moreover, the device employing 0.2-μm gate length also achieves a significant saturation output current density (IDMAX) of 0.94 A/mm, a high peak transconductance (GmMAX) of 577.6 mS/mm and a power gain cut-off frequency (fMAX) of 138 GHz. At 18 GHz, a record power-added-efficiency (PAE) of 70% associated with a high output power density of 2.22 W/mm is realized in a continuous-wave (CW) mode at VDS = 12 V. The improved performance of E-mode GaN HEMTs supplying the inverted trapezoidal recessed-gate demonstrates a great potential in Low-Supply-Voltage RF terminal applications.