High performance 0.35 μm gate-length monolithic enhancement/depletion-mode metamorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As HEMTs on GaAs substrates

Monolithic integration of enhancement (E)- and depletion (D)-mode metamorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As/GaAs HEMTs with 0.35 μm gate-length is presented for the first time. Epilayers are grown on 3-inch SI GaAs substrates using molecular beam epitaxy. A mobility of 9550 cm
²
/V-s and a sheet density of 1.12×10/sup 12/ /sup -2/ are achieved at room temperature. Buried Pt-gate was employed for E-mode devices to achieve a positive shift in the threshold voltage. Excellent characteristics are achieved with threshold voltage, maximum drain current, and extrinsic transconductance of 100 mV, 370 mA/mm and 660 mS/mm, respectively for E-mode devices, and -550 mV, 390 mA/mm and 510 mS/mm, respectively for D-mode devices. The unity current gain cutoff frequencies of 75 GHz for E-mode and 80 GHz for D-mode are reported.