Power performance of microwave high-electron mobility transistors

The large-signal performance of 0.25-µm gate-length high-electron mobility transistors (HEMT's) operating at 15 GHz is reported. At a drain voltage of 5 V, an output power of 135 mW (0.34 W/mm) has been obtained with 8-dB associated gain and 37-percent power-added efficiency. Furthermore, in class C operation a power-added efficiency of 57 percent has been measured. These results are attributed to high transconductance (300 mS/mm), high gain (12-dB maximum stable gain at 18 GHz), low knee voltage (1.25 V), relatively high full channel current (280 mA/mm at
V_{ds} = 2
V), and good RF drain-source breakdown voltage (9 V).