AlN/GaN/InGaN Coupling-Channel HEMTs for Improved <i>g</i> _<i>m</i> and Gain Linearity

Abstract

In this article, we report on the effective transconductance ( g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) and gain linearity improvement of submicrometer gate AlN-barrier-based transistors using GaN/InGaN coupling-channel structures. The fabricated AlN/GaN/InGaN coupling-channel high electron mobility transistor (CC-HEMT) showed flat g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> profile, greatly reduced g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> derivatives, and constant dynamic source resistance compared with an AlN/GaN HEMT using the same fabrication process. The highest extrinsic 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 55 GHz and the maximum oscillation frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) of 80 GHz were obtained for 0.15- μm gate-length transistors, both of which remain constant values across wide input voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> ) of 4 V. Moreover, a significant theoretical OIP3 value boost by 7.1 dB has been observed using the CC-HEMT as compared to the AlN/GaN HEMT. The superior linearity performance of the CC-HEMT can be attributed to the strong channel-to-channel coupling effect. The drain bias-dependence of g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , 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> versus V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> profiles illustrate that the linearity characteristics of the CC-HEMT greatly improve with an increase in V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> . These results demonstrate the AlN/GaN/InGaN material system as a viable platform for high frequency requiring high-linearity applications.