A Comprehensive Study on Recess Gated Fe-Doped AlN/GaN/AlGaN HEMT for Next Generation Broadband Power Amplifiers

The effect of gate recess on DC/RF performance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{L}_{\mathbf{G}}=200$</tex> nm AlN/GaN/AlGaN HEMT on SiC wafer is compared with the performance of the nonrecessed device. When compared to the non-recess HEMT structure, the L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</inf> = 200nm device has a substantial peak G<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> of 1339 mS/mm & a peak I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf> of 3.29 A/mm at 2nm recess depth. The results also revealed the trade-off between positive shift of V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</inf> and output drain current beyond 2nm recess depth. Besides recess depth, the work function-dependent performance of the device is explored at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{L}_{\mathbf{rec}}=2\mathbf{nm}$</tex>, an optimal recess depth. The simulation results show that electrical characteristics are dependent on the work function of gate metal. Finally, the investigation carried out to examine the effects of Fe-doped AlGaN buffer showed excellent DC/RF characteristics. When compared with the undoped AlGaN buffer, the Fe-doped AlGaN buffer device exhibited the highest I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf> of 3.48 A/mm, & peak G<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> of 1336 mS/mm, and an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{f}_{\mathbf{T}}$</tex> of 69.8 GHz. Our device with Fe-doped AlGaN buffer at an optimized recess depth of 2 nm has been demonstrated to be a potential choice for beyond 5G applications.