DC and RF characteristics of InAlAs/In0.7Ga0.3As HEMTS at 16 K

DC and RF characteristics at 300 and 16 K of In_0.52Al_0.48As/In_0.7Ga_0.3As high electron mobility transistors (HEMTs) were measured in the gate length L_g range of 50 to 700 nm. The maximum drain-source current I_ds and the maximum transconductance g_{m_max} increased at 16 K as expected. We observed an increase of 21 to 36% in the value of the cutoff frequency f_T at 16 K over that at 300 K. Furthermore, we measured f_T 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 f_T exceeded 600 GHz at 16 K. Even at a drain-source voltage V_ds of 0.4 V, we obtained an f_T of 500 GHz at 16 K.