Fabrication of 150-nm Al0.48In0.52As/Ga0.47In0.53As mHEMTs on GaAs substrates

High performance 150-nm gate-length metamorphic Al0.48In0.52As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) with very good device performance have been successfully fabricated. A T-shaped gate is fabricated by using a combined technique of optical and e-beam photolithography, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate. The ohmic contact resistance R (c) is as low as 0.03 Omega.mm when using a novel ohmic contact metal system (Ni/Ge/Ti/Au). The devices exhibit excellent DC and RF performance. A peak extrinsic transconductance of 775 mS/mm and a maximum drain current density of 720 mA/mm are achieved. The unity current gain cut-off frequency (f (T) ) and the maximum oscillation frequency (f (max)) are 188.4 and 250 GHz, respectively.