30-nm InAs Pseudomorphic HEMTs on an InP Substrate With a Current-Gain Cutoff Frequency of 628 GHz

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We report on InAs pseudomorphic high-electron mobility transistors (PHEMTs) on an InP substrate with record cutoff frequency characteristics. This result was achieved by paying attention to minimizing resistive and capacitive parasitics and improving short-channel effects, which play a key role in high-frequency response. Toward this, the device design features a very thin channel and is fabricated through a three-step recess process that yields a scaled-down barrier thickness. A 30-nm InAs PHEMT with <formula formulatype="inline"><tex Notation="TeX">$t_{\rm ins} = \hbox{4}\ \hbox{nm}$</tex></formula> and <formula formulatype="inline"><tex Notation="TeX">$t_{\rm ch} = \hbox{10}\ \hbox{nm}$</tex> </formula> exhibits excellent <formula formulatype="inline"><tex Notation="TeX">$g_{m, \max}$</tex></formula> of 1.62 S/mm, <formula formulatype="inline"><tex Notation="TeX">$f_{T}$</tex></formula> of 628 GHz, and <formula formulatype="inline"><tex Notation="TeX">$f_{ \max}$</tex></formula> of 331 GHz at <formula formulatype="inline"><tex Notation="TeX">$V_{\rm DS} = \hbox{0.6}\ \hbox{V}$</tex> </formula>. To the knowledge of the authors, the obtained <formula formulatype="inline"><tex Notation="TeX">$f_{T}$</tex></formula> is the highest ever reported in any FET on any material system. In addition, a 50-nm device shows the best combination of <formula formulatype="inline"><tex Notation="TeX">$f_{T} = \hbox{557}\ \hbox{GHz}$</tex></formula> and <formula formulatype="inline"><tex Notation="TeX">$f_{\max} = \hbox{718}\ \hbox{GHz}$</tex></formula> of any transistor technology. </para>