High RF performance of 50-nm-gate lattice-matched InAlAs/InGaAs HEMTs

We fabricated 50-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates by using a conventional process under low temperatures, below 300 degreesC, to prevent fluorine contamination and suppress possible diffusion of the Si-delta -doped sheet in the electron-supply layer, and measured the DC and RF performance of the transistors. The DC measurement showed that the maximum transconductance g(m) of a 50-nm-gate HEMT is about 0.91 S/mm. The cutoff frequency f(T) of our 50-nm-gate HEMT is 362 GHz, which is much higher than the values reported for previous 50-nm-gate lattice-matched HEMTs. The excellent RF performance of our HEMTs results from a shortening of the lateral extended range of charge control by the drain field, and this may have been achieved because the low-temperature fabrication process suppressed degradation of epitaxial structure.