Abstract
This paper describes the device fabrication process and characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) aimed for millimeter-wave applications. We developed three novel techniques to suppress short-channel effects and thereby enhance high-frequency device characteristics: high-Al-composition and thin AlGaN barrier layers, SiN passivation by catalytic chemical vapor deposition, and sub-100-nm Ti-based gates. The Al0.4Ga0.6N/GaN HFETs with a gate length of 30nm had a maximum drain current density of 1.6A/mm and a maximum transconductance of 402mS/mm. The use of these techniques led to a current-gain cutoff frequency of 181GHz and a maximum oscillation frequency of 186GHz.
