Gate-metal formation-related kink effect and gate current on In0.5Al0.5As∕In0.5Ga0.5As metamorphic high electron mobility transistor performance

Abstract

In 0.5 Ga 0.5 As ∕ In 0.5 Al 0.5 As metamorphic high electron mobility transistos were fabricated with different gate-metal formations: mesa type or air type and without or with a buried gate. Only air-type devices with a buried gate show no kink effect. Experimental results indicate that gate-feeder metal and annealing process give effects on gate current and noise figure. The peak gate current of 12 (120)μA∕mm for air-type (mesa-type) devices before annealing is improved to 8 (55)μA∕mm after annealing. At 1.8GHz, associated gain of 25dB is obtained at Fmin=1.24dB for air-type devices after annealing, while 23dB is obtained at Fmin=1.25dB before annealing.