DC and RF characteristics of InAlAs/In<inf>0.7</inf>Ga<inf>0.3</inf>As HEMTS at 16 K

Abstract

DC and RF characteristics at 300 and 16 K of In0.52Al0.48As/In0.7Ga0.3As high electron mobility transistors (HEMTs) were measured in the gate length Lg range of 50 to 700 nm. The maximum drain-source current Ids and the maximum transconductance gm_max increased at 16 K as expected. We observed an increase of 21 to 36% in the value of the cutoff frequency fT at 16 K over that at 300 K. Furthermore, we measured fT values at 16 K of a 30-nm-gate HEMT that had a multi-layer cap structure to reduce source and drain resistances under various bias conditions. The maximum fT exceeded 600 GHz at 16 K. Even at a drain-source voltage Vds of 0.4 V, we obtained an fT of 500 GHz at 16 K.