0.1-μm p+-GaAs gate HJFETs with fT=121 GHz fabricated using all dry-etching and selective MOMBE growth

This paper reports the first successful fabrication of a high-performance, 0.1-μm, T-shaped, p⁺-gate pseudomorphic heterojunction-FET (HJFET) using all dry-etching and selective MOMBE growth techniques. We have developed a two-step dry-etching technique that compensates for the poor dry-etching resistance of PMMA, and a voidless gate-electrode filling technique for high aspect-ratio openings with selective MOMBE p⁺-GaAs growth. Our efforts results in a reduction of external gate fringing capacitance and a improvement in gate turn-on voltage. The fabricated 0.1-μm, p⁺-gate n-Al _0.2Ga_0.8As-In_0.25Ga_0.75As HJFET exhibits excellent microwave performance, f_T=121 GHz and f_max=144 GHz