220GHz f<inf>T</inf> and 400GHz f<inf>max</inf> in 40-nm GaN DH-HEMTs with re-grown ohmic

Abstract

We report record RF performance in 40nm-gate GaN-HEMT technology. Through vertical scaling in an AlN/GaN/AlGaN double heterojunction (DH) HEMT structure and reduction of access resistance using MBE re-growth of n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -GaN ohmic contacts, fully-passivated 40-nm devices exhibited excellent DC characteristics, such as an R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> of 0.81Ω·mm, an I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dmax</sub> of 1.61A/mm, a BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> of 42V, and a peak extrinsic g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> of 723mS/mm, resulting in a peak f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of 220GHz and a peak f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 400GHz. The measured f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> are the highest ever reported in a GaN-HEMT technology. Small signal model and delay time analysis showed that the parasitic charging time was only 10% of total delay time and the gate transit time scaled with the gate length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) down to 40nm, demonstrating high scalability of the new technology.