Deeply-scaled self-aligned-gate GaN DH-HEMTs with ultrahigh cutoff frequency

Abstract

We report record DC and RF performance in deeply-scaled self-aligned gate (SAG) GaN-HEMTs operating in both depletion-mode (D-mode) and enhancement-mode (E-mode). Through aggressive lateral scaling of the gate length (L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</inf> ) and the source-drain distance (L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sd</inf> ) using a novel self-aligned gate technology and engineering of a thin top barrier layer, 20-nm gate AlN/GaN/AlGaN double-heterojunction (DH) HEMTs operating in D-mode (and E-mode) exhibited record DC and RF characteristics with high yield and uniformity; R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</inf> = 0.29 (0.33) Ω·mm, I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dmax</inf> = 2.7 (2.6) A/mm, a peak extrinsic g <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> = 1.04 (1.63) S/mm, threshold voltage uniformity σ (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> ) = 44 (63) mV over a 3-inch wafer area, and a simultaneous f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> /f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> = 310/364 (343/236) GHz. Delay time analysis clarified that an unique dependence of f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> on V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</inf> resulted from suppressed drain delay and enhanced electron velocity due to the lateral source-drain (S-D) scaling.