AlGaN/GaN HEMTs on Silicon Substrate With 206-GHz $F_{ \rm MAX}$

This letter reports on AlGaN/GaN high-electron-mobility transistors (HEMTs) on high-resistive silicon substrate with a record maximum oscillation cutoff frequency <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> . Double-T-shaped gates are associated with an optimized technology to enable high-efficiency 2-D electron gas control while mitigating the parasitic resistances. Good results ogate-length HEMTf <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> = 206 GHz and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FT</i> = 100 GHz are obtained for a 90-nm gate-length HEMT with 0.25-μm source-to-gate spacing. The associated peak extrinsic transconductance value is as high as 440 mS·mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . To the authors' knowledge, the obtained <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Gm</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ext</sub> are the highest reported values for GaN HEMTs technology on silicon substrate. The accuracy of the cutoff frequency values is checked by small-signal modeling based on extracted S-parameters.