RF parametric study on AlGaN/GaN HEMTs on Si-substrate for millimeter-wave PA

Size-optimized AlGaN/GaN HEMTs on Si-substrate are investigated for millimeter-wave power amplifier (PA) MMICs. The number of finger (2, 4, 8) and the unit finger width (25, 37.5, 50, 75, 100 μm) of devices are split in the AlGaN/GaN HEMTs process on Si-substrate. For searching the best suitable size for millimeter-wave PA, the RF performances such as F_max and MAG (Maximum Available Gain) are investigated through S-parameter measurements and small signal model parameter extractions. Moreover, thermal resistances are extracted through pulsed IV measurement to evaluate thermal degradation on GaN HEMTs. Through these experiments and parametric analyses, 4×37.5 μm or 8 × 37.5 μm GaN HEMTs show the best RF performance keeping not larger thermal resistances (Rth). Thermal resistance and MAG are dependent on the gate pitch of GaN HEMTs. The selection of the proper gate pitch parameter of device is expected to bring the optimal power device performance in the millimeter-wave frequencies.