Comparative Analysis of T-gate GaN HEMT with different passivation layers for RF Applications

In this work, we investigate the impact of various passivation layers on electrical characteristics of T-gate GaN HEMT. Passivation schemes with single passivation layer of SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, and stacked HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with and without air gap have been investigated. The air gap between the gate and the low-k passivation layer effectively reduces the gate capacitance, thereby enhancing the RF characteristics of the device. A 200 nm gate length and 100 μm width are used to simulate the device. The passivation layer of SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with air gap, due to improved transconductance and gate capacitances exhibits a cut-off frequency of 39.22 GHz and a maximum oscillation frequency of 51.6 GHz. Results clearly shows that AlGaN/GaN HEMT having SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with an air gap is most suitable for RF applications.