InAlN/AlN/GaN HEMTs With Regrown Ohmic Contacts and $f_{T}$ of 370 GHz

Abstract

We report 30-nm-gate-length InAlN/AlN/GaN/SiC high-electron-mobility transistors (HEMTs) with 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 370 GHz. The HEMT without back barrier exhibits an extrinsic transconductance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(g_{\rm m.ext})$</tex></formula> of 650 mS/mm and an on/off current ratio of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$10^{6}$</tex></formula> owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Omega\cdot\hbox{mm}$</tex></formula> . Delay analysis suggests that the high <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> is a result of low gate–drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHz <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> by further reducing the gate length, it is imperative to investigate alternative structures that offer higher mobility/velocity while keeping the best possible electrostatic control in ultrascaled geometry.