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

In this paper, an enhancement-mode (E-mode) GaN high electron mobility transistors (HEMTs) with an innovational inverted trapezoidal recessed-gate is successfully fabricated by using a developed variable pressure gate etching process, which contributes to a 0.41 V positive threshold voltage (VTH) and a significant saturation output current density (IDMAX) of 0.94 A/mm. the device employing 0.2-µm T-gate length exhibits 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. Compared with others E-mode structure, the improved E-mode GaN HEMTs demonstrates a great potential in Low-Supply-Voltage RF terminal applications.