35-nm-Gate In0.7Ga0.3As/In0.52Al0.48As HEMT with 520-GHz fT

We fabricated a 35-nm-gate In_0.7Ga_0.3As/In_0.52Al_0.48As high electron mobility transistor by using a simple, self-aligned one-step-recessed gate procedure. An extrinsic maximum transconductance (g_{m_max}) of 1.7 S/mm and a current gain cutoff frequency (f_T) of 520 GHz were achieved at room temperature. This significantly high f_T was obtained by reducing the gate length to 35 nm and using an epitaxial structure with a 3-nm-thick InAlAs spacer layer, a 6-nm-thick InAlAs Schottky barrier layer and a 2-nm-thick InP etching stopper layer to decrease the gate-to-channel distance to 8 nm, and form simultaneously 50-nm-long side-recess structures and T-shaped gates stacked on the InAlAs Schottky barrier layer. These results are the first experimental achievement of f_T as high as 520 GHz by using the one-step-recessed gate procedure.