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A method is reported for capless annealing of ion-implanted GaAs which gives electrical activation of Se-implanted wafers nearly identical to that obtained with sputtered silicon nitride caps. State-of-the-art performance has been realized from Schottky-gate FET’s fabricated from this material.

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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 µm × 25 µm via holes on substrates thinned to 1 mil, we achieved a 13.5 dB maximum stable gain (MSG) at 110 GHz for a 30-µm 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.Index Terms-Electron beam lithography, high electronmobility transistors (HEMTs), maximum stable gain (MSG), metamorphic HEMTs (MHEMTs), MODFETs, submillimeter wave FETs.