Dual-gate AlGaN/GaN high-electron-mobility transistors with short gate length for high-power mixers

We have fabricated dual-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) with a short gate on SiC substrates for use in high-power mixers and have measured the DC and up-conversion RF characteristics. A device with a T-shaped gate (0.15 um × 300 μm) exhibits a maximum transconductance of 40 mS, an on-state breakdown voltage of over 30 V, and off-state breakdown voltage of 86 V. The maximum RF output power (P_RFout) is 17 dBm, and the up-conversion gain is 7.5 dB at a frequency of 10 GHz when the bias point voltage is 30 V. As the local frequency increases from 2 to 10 GHz, P _RFout and the gain decrease by only 2 and 2.6 dB, respectively. Shortening the gate was found to be effective in improving the frequency characteristics of a mixer at frequencies up to and including the X-band.