Enhancement of $f_{\mathrm {max}}$ to 910 GHz by Adopting Asymmetric Gate Recess and Double-Side-Doped Structure in 75-nm-Gate InAlAs/InGaAs HEMTs

Abstract

A high maximum frequency of oscillation ( $f_{\mathrm {{max}}}$ ) of 910 GHz was achieved at InAlAs/InGaAs high-electron mobility transistors (HEMTs) with a relatively long gate length ( $L_{G}$ ) of 75 nm by adopting an asymmetric gate recess and a double-side-doped structure. The $f_{\mathrm {{max}}}$ improved significantly by extending the drain-side gate recess length ( $L_{\mathrm {{RD}}}$ ) to 250 nm; meanwhile, the source-side gate-recess length ( $L_{\mathrm {{RS}}}$ ) was kept to 70 nm. The improvement in $f_{\mathrm {{max}}}$ was due to a decrease in the drain output conductance ( $g_{d}$ ) and drain-to-gate capacitance ( $\text{C}_{\mathrm {{GD}}}$ ) after the extension of $L_{\mathrm {{RD}}}$ . $g_{d}$ was further suppressed by applying a double-side-doped structure to the InP-based HEMTs. A reduction in $g_{d}$ resulted in a drastic improvement in $f_{\mathrm {{max}}}$ even though $L_{G}$ was a longer value.