Logic Suitability of 50-nm $\hbox{In}_{0.7} \hbox{Ga}_{0.3}\hbox{As}$ HEMTs for Beyond-CMOS Applications

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We have experimentally studied the suitability of nanometer-scale <formula formulatype="inline"><tex>$ \hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$</tex></formula> high-electron mobility transistors (HEMTs) as an n-channel device for a future high-speed and low-power logic technology for beyond-CMOS applications. To this end, we have fabricated 50- to 150-nm-gate-length <formula formulatype="inline"><tex>$\hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$ </tex></formula> HEMTs with different gate stack designs. This has allowed us to investigate the role of Schottky barrier height <formula formulatype="inline"><tex>$(\Phi_{B})$</tex></formula> and insulator thickness <formula formulatype="inline"><tex>$(t_{\rm ins})$</tex></formula> on the logic characteristics of <formula formulatype="inline"><tex>$\hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$</tex></formula> HEMTs. The best 50-nm HEMTs with the highest <formula formulatype="inline"><tex>$\Phi_{B}$</tex></formula> and the smallest <formula formulatype="inline"><tex>$t_{\rm ins}$</tex></formula> exhibit an <formula formulatype="inline"><tex>$I_{ \rm ON}/I_{\rm OFF}$</tex></formula> ratio in excess of <formula formulatype="inline"><tex>$\hbox{10}^{4}$</tex> </formula> and a subthreshold slope <formula formulatype="inline"><tex>$(S)$</tex></formula> below 86 mV/dec. These nonoptimized 50-nm <formula formulatype="inline"><tex>$\hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$</tex></formula> HEMTs also show a logic gate delay <formula formulatype="inline"><tex>$(CV/I)$</tex></formula> of around 1 ps at a supply voltage of 0.5 V, while maintaining an <formula formulatype="inline"><tex>$I_{\rm ON}/I_{\rm OFF}$</tex> </formula> ratio above <formula formulatype="inline"><tex>$\hbox{10}^{4}$</tex></formula>, which is comparable to state-of-the-art Si MOSFETs. As one of the alternatives for beyond-CMOS technologies, we believe that InAs-rich InGaAs HEMTs hold a considerable promise. </para>