360 GHz fMAX Graded-Channel AlGaN/GaN HEMTs for mmW Low-Noise Applications

Abstract

We report scaled, graded-channel AlGaN/GaN HEMTs with an extrinsic 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> of 170 GHz and 363 GHz, which is the highest in emerging graded-channel GaN HEMTs. At 50-nm gate length, the f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ·Lg of 8.5 GHz·μm is comparable to that of conventional scaled AlGaN/GaN HEMTs fabricated together. At low DC power, the scaled graded-channel AlGaN/GaN HEMTs show a higher f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> than the scaled AlGaN/GaN HEMT with the same gate length. The devices also exhibit a 2 dB improvement in gain at low DC bias, and the measured minimum noise figure was as low as 0.5 dB at 30 GHz. This is comparable to state-of-the-art device noise figure from a 20-nm gate length AlGaN/GaN HEMT. The combination of improved f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> , f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> , and minimum noise figure at low DC power for the graded-channelAlGaN/GaN HEMTs shows great promise for ultra-low-power, low-noise amplifiers.