Asymmetrically recessed 50-nm gate-length metamorphic high electron-mobility transistor with enhanced gain performance

We report the design, fabrication and characterization of ultrahigh gain metamorphic high electron-mobility transistors. In this letter, a high-yield 50-nm T-gate process was successfully developed and applied to epitaxial layers containing high indium mole fraction InGaAs channels grown on GaAs substrates. A unique gate recess process was adopted to significantly increase device gain by effectively suppressing output conductance and feedback capacitance. Coupled with extremely small 10 mu m x 25 mu m via holes on substrates thinned to 1 mil, we achieved a 13.5 dB maximum stable gain (MSG) at 110 GHz for a 30-mu m gate-width device. To our knowledge, this is the highest gain performance reported for microwave high electron-mobility transistor devices of similar gate periphery at this frequency, and equivalent circuit modeling indicates that this device will operate at frequencies beyond 300 GHz.