Comparative Study of DC and Microwave Characteristics of 0.12 µm Double-Recessed Gate AlGaAs/InGaAs/GaAs Pseudomorphic High-Electron-Mobility Transistors Using Dielectric-Assisted Process

Abstract

We report the fabrication and DC and microwave characteristics of 0.12 µm double-recessed T-gate AlGaAs/InGaAs/GaAs pseudomorphic high-electron-mobility transistors (PHEMTs) using dielectric-assisted process. Silicon nitride layers 300 and 200 Å thick were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 260 °C to protect the device and to define the gate footprint. The double-recess process was carried out by two different etching techniques to obtain double-recessed T-gates with 0.12 µm gate lengths. Completed double-recessed T-gate AlGaAs/InGaAs/GaAs pHEMT devices fabricated using dry etching exhibited a peak transconductance, gm, of 765 mS/mm, a current-gain cutoff frequency ( fT) as high as 124 GHz, and a maximum oscillation frequency ( fmax) of 247 GHz. The fabricated low-noise amplifier (LNA) has a measured gain of more than 20 dB in the 62.75 to 64.75 GHz frequency range.