220-GHz Quaternary Barrier InAlGaN/AlN/GaN HEMTs

Abstract

Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{In}_{0.13}\hbox{Al}_{0.83}\hbox{Ga}_{0.04}\break\hbox{N/AlN/GaN}$</tex> </formula> heterostructure on SiC substrate were fabricated. The 66-nm-long gate device shows a dc drain current density of 2.1 A/mm, a peak extrinsic transconductance of 548 mS/mm, and a record current gain cutoff frequency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f_{T}$</tex></formula> of 220 GHz for quaternary barrier GaN-based HEMTs, which is also among the highest <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f_{T}$</tex></formula> for all GaN-based HEMTs. The large <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$L_{g} \cdot f_{T}$</tex></formula> product of 14.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{GHz} \cdot \mu\hbox{m}$</tex></formula> with a gate-length-to-barrier-thickness aspect ratio of 5.8 indicates a high effective electron velocity of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{0.9} \times \hbox{10}^{7}\ \hbox{cm/s}$</tex></formula> , attributed to a high electron Hall mobility (1790 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{cm}^{2}/\hbox{V} \cdot \hbox{s}$</tex> </formula> at an <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n_{s}$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{1.8} \times \hbox{10}^{13}\ \hbox{cm}^{-2}$</tex></formula> )—the highest reported in GaN-channel HEMTs with In-containing barriers. An intrinsic electron velocity of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1.7} \times \hbox{10}^{7}\ \hbox{cm/s}$</tex></formula> , extracted from conventional Moll delay-time analysis, is comparable to that reported in the state-of-art AlGaN/GaN HEMTs.