Hf_0.5Zr_0.5O₂-Based Ferroelectric Gate HEMTs With Large Threshold Voltage Tuning Range

Abstract

AlGaN/GaN high-electron-mobility transistors (HEMTs) with Hr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ferroelectric gate stacks exhibiting significant ferroelectric switching for threshold voltage control are experimentally demonstrated. Ferroelectric gate HEMTs (FeHEMTs) with large threshold voltage tuning range of 2.8 V were obtained, with an on/off ratio of ~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> based on a GaN-channel HEMT structure suitable for RF applications. Improved subthreshold performance has also been achieved compared to conventional MIS-HEMTs, with reduction in average sub-threshold swing (SS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> ) by a factor of 2. As a consequence of the significant ferroelectric polarization achieved on AlGaN/GaN heterostructures, Hr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based ferroelectric gate AlGaN/GaN HEMTs appear promising for nonvolatile and reconfigurable RF and microwave applications.