Fabrication technology and device performance of sub-50-nm-gate InP-based high electron mobility transistors

We fabricated sub-50-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates. The two-step-recessed gate technology and low-temperature process, with all steps taking place below 300degreesC, allowed us to fabricate sub-50-nm-gate HEMTs that had high levels of performance. We succeeded in fabricating ultrashort 25-nm-long T-shaped gates. DC measurements showed that the 25-nm-gate HEMT had good pinchoff behavior, and that its maximum transconductance g(m) was about 770 mS/mm. A cutoff frequency f(T) of 396 GHz was obtained for the 25-nm-gate HEMT. This f(T) is the highest value yet reported for a transistor of any type, and the gate length of 25 nm is the shortest value ever reported for any compound semiconductor transistor that exhibits true device operation.