Monolithic Integration of E/D-Mode AlGaN/GaN MIS-HEMTs

Monolithic integration of enhancement/depletion (E/D)-mode AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) are demonstrated for mixed signal applications. The gate length for the E-mode and D-mode devices are 0.2 μm and 0.35 μm, respectively, and drain current of 496 (Vgs=+5 V) and 720 mA/mm (Vgs=0 V) with a peak transconductance of 147 and 131 mS/mm are measured. Small-signal measurements result matched current-gain cutoff frequency (fT)/maximum oscillation frequency (fmax) of 29.9/55.2 GHz for the E-mode and 27.5/47.5 GHz for the D-mode devices. Direct-coupled FET logic E/D MIS-HEMT inverter and 51-stage ring oscillator are fabricated. The incorporation of gate dielectric enables the inverter a large logic voltage swing of 3.71 V at a supply voltage VDD of 5 V. The 51-stage ring oscillator implemented with 106 transistors shows an oscillation frequency of 427.6 MHz at VDD=5 V, corresponding to a stage delay of 23 ps.