High-power stable field-plated AlGaN-GaN MOSHFETs

We describe novel AlGaN-GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with record high power-voltage efficiencies (PVE = RF power/Drain bias), up to 0.43W/V-mm at 2 GHz. The RF powers of 15 W/mm at 35 V (PVE=0.43 W/V-mm) and 20 W/mm at 55 V (PVE= 0.36W/V-mm) were measured, which are approximately 50% higher than the previously reported values of PVE=0.25 W/V-mm (30 W/mm at 120 V). The MOSHFET devices exhibit an extremely stable operation for times in excess of 120 hours at power levels close to 20 W/mm. This is also the first demonstration of stability for a III-N microwave FET device at such a high power level. The key features of our new device design are (i) current collapse-free operation using trapped charge removing field-plates over leaky dielectric layers; (ii) selective area doping to achieve record low access resistances and (iii) an insulated gate design suppressing forward gate currents responsible for device degradation. In the paper we will present detailed experimental evidence to support our explanations for achieving the record RF-performance for the III-N FETs for the first time