Ultra-short T-shaped gate fabrication technique for sub-millimeter-wave InP-HEMTs: optimization of process conditions

摘要

InP-based InGaAs/InAlAs high electron mobility transistors (HEMTs) are considered to be one of the most promising devices for millimeter-wave radio communications because of their superior high frequency and low-noise performances. This is due to high electron mobility, high saturation velocity, and high sheet carrier density obtained in this system. A shorter gate is also essential for ultra-high RF performances. In our previous work, RF performances have been significantly improved by reducing gate length (L{sub}g) down to 50 nm using a simple lift-off process and a low temperature process. In this paper, we have developed a sub-50-nm T-shaped-gate fabrication technique using a conventional tri-layer resist system by optimizing electron beam (EB) lithography and reactive ion etching (RIE) conditions, demonstrating a cutoff frequency (f{sub}T) as high as 318 GHz in a 35-nm-gate HEMT.