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 (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m,max</sub> ) of 1.65 S/mm and a current gain cutoff frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of 610 GHz for 15-nm-gate HEMTs on GaAs substrates. Through a delay time analysis, the ultrahigh f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of this work is explained by an enhanced average electron velocity under the gate (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ave</sub> ) of 4.3 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> cm/s, which was a result of reduction of gate length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) and epitaxial engineering. This report is the first experimental demonstration of 15 nm InAlAs/TnGaAs metamorphic HEMTs (MHEMTs) with an extremely high f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of 610 GHz.