A heterostructure FET with 75.8-percent power added efficiency at 10 GHz

The authors report the performance of a new AlGaAs/GaAs heterostructure FET (HFET) designed to have very high efficiency at the X-band with high drain bias. The combination of low doped AlGaAs under the gate and highly doped GaAs channel and superlattice buffer layers allows high gate-drain and source-drain breakdown voltage, constant transconductance, and moderate-to-high maximum channel current. These characteristics make the devices ideal for Class B and Class F operation. The 1200*0.25- mu m HFET devices have demonstrated a power-added efficiency (PAE) of 75.8% with 603 mW of output power and 8.8 dB of gain with a 9-V drain bias at 10 GHz. Other 1200*0.25- mu m HFET devices have demonstrated a 63.2% PAE with 8.3 dB of gain and 851 mW of output power with a 12-V drain bias. At 14 volts, 50% PAE was measured with 7.4-dB gain and 1.1 W of output power.<>