A Millimeter-Wave AlGaN/GaN HEMT Fabricated With Transitional-Recessed-Gate Technology for High-Gain and High- Linearity Applications

Abstract

A high-linearity and high-gain AlGaN/GaN HEMTs with a 100-nm gate were demonstrated. The device employs transitional recessed gate (TRG) along the gate width for millimeter wave power application. The gradually changing gate recess depth was created using transitional dosed photoetching. Accurate etching ensured that the FET-elements have a continued V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ts</sub> offset in the local equivalent threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) in different areas. The device exhibits a high I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d,max</sub> of 1.12 A/mm and a high peak extrinsic gm of 374 mS/mm with an improved gate swing > 2.6 V, much higher than that of Fin-HEMT. Excellent RF performance was shown, including 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> = 61.8/148.8 GHz, G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">as</sub> /G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">linear</sub> = 9.98/ 12dB at 30 GHz. To the best of our knowledge, this is the best associated gain and linearity performance reported to date for AlGaN/GaN HEMTs. This letter has great potential for high gain and linearity millimeter wave power applications, which are needed for future communication systems.