Fabrication of 80-nm T-gate high indium In 0.7 Ga 0.3 As/In 0.6 Ga 0.4 As composite channels mHEMT on GaAs substrate with simple technological process

An 80-nm gate length metamorphic high electron mobility transistor (mHEMT) on a GaAs substrate with high indium composite compound-channels In 0.7 Ga 0.3 As/In 0.6 Ga 0.4 As and an optimized grade buffer scheme is presented. High 2-DEG Hall mobility values of 10200 cm 2 /(V· s) and a sheet density of 3.5 × 10 12 cm -2 at 300 K have been achieved. The device's T-shaped gate was made by utilizing a simple three layers electron beam resist, instead of employing a passivation layer for the T-share gate, which is beneficial to decreasing parasitic capacitance and parasitic resistance of the gate and simplifying the device manufacturing process. The ohmic contact resistance R c is 0.2 Ω ·mm when using the same metal system with the gate (Pt/Ti/Pt/Au), which reduces the manufacturing cycle of the device. The mHEMT device demonstrates excellent DC and RF characteristics. The peak extrinsic transconductance of 1.1 S/mm and the maximum drain current density of 0.86 A/mm are obtained. The unity current gain cut-off frequency ( f T ) and the maximum oscillation frequency ( f max ) are 246 and 301 GHz, respectively.