610 GHz InAlAs/In<inf>0.75</inf>GaAs Metamorphic HEMTs with an Ultra-Short 15-nm-Gate

Abstract

Ultra-short-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) have been successfully fabricated with nano-gate fabrication technology and epitaxial optimization. We obtained an extrinsic maximum transconductance (Gm,max) of 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 time analysis, the ultrahigh fT of this work is explained by an enhanced average electron velocity under the gate (Vave) of 4.3 x 107 cm/s, which was a result of reduction of gate length (Lg) and epitaxial engineering. This report is the first experimental demonstration of 15 nm InAlAs/TnGaAs metamorphic HEMTs (MHEMTs) with an extremely high fT of 610 GHz.