by high aspect ratio of T-shaped gate. Moreover, epitaxial Ultra-short-gate InAlAs/InGaAs high electron mobility engineering was simultaneously applied to make the reduction transistors (HEMTs) have been successfully fabricated with of Lg to be effective. nano-gate fabrication technology and epitaxial optimization. We Device structure and fabrication technology obtained an extrinsic maximum transconductance (GmmaX) of The epitaxial and gate structure of the InAlAs/1no75GaAs 1.65 S/mm and a current gain cutoff frequency (fT) of 610 GHz for 15-nm-gate HEMTs on GaAs substrates. Through a delay grown is d in Fig. 1. Thecular lay ere time analysis, the ultrahigh fT of this work is explained by an grown o aeGaAs sub strat y l ar beam nel of enhanced average electron velocity under the gate (Uave) of 4.3 x 7 CM/S, which was a result ofreduction of gate length (Lg and pseudomorphic HIEMT structure. The motivation was to epitaxial engineering. This report is the first experimental improve device characteristics such as current drive demonstration of 15 nm InAlAs/InGaAs metamorphic HEMTs capabilities, transconductance (Gm), and RF performance (MUEMTs) with an extremely high fTof610 GHz.through an enhancement of transport property at the channel [6]. The reduction of compressive strain was realized by