Dual-Gate E/E- and E/D-Mode AlGaAs/InGaAs pHEMTs for Microwave Circuit Applications

In this paper, we developed dual-gate enhancement/enhancement-mode (E/E-mode) and enhancement/depletion-mode (E/D-mode) AlGaAs/InGaAs pHEMTs for high-voltage and high-power device applications. These dual-gate devices had a higher breakdown voltage (V_br) and maximum oscillation frequency (f_max). This could be obtained because there were two depletion regions, and the total electrical field was shared between the two regions, leading to lower output conductance (g_o) and lower gate-to-drain capacitance (C_gd). The dual-gate device can be operated at a higher drain-to-source voltage (V_ds), resulting in better linear gain and output power performance, as compared to a conventional single-gate E-mode GaAs pHEMT device. The maximum oscillation frequency obtained using the dual-gate E/E-mode device increased from 78 to 123 GHz. When operated at 2.4 GHz, the maximum RF output power of the single-gate E-mode and dual-gate E/D-mode devices increased from 636 to 810 mW/mm, respectively. We also produced a 2.4-GHz high-gain and high-power density two-stage power amplifier using dual-gate E/E and E/D-mode transistors. A linear gain of 40 dB and a maximum output power of 24 dBm were obtained.