50-NM SELF-ALIGNED-GATE PSEUDOMORPHIC ALINAS GAINAS HIGH ELECTRON-MOBILITY TRANSISTORS

We report on the design and fabrication of a new class of 50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs High Electron Mobility Transistors (HEMT's) with potential for ultra-high-frequency and ultra-low-noise applications. These devices exhibit an extrinsic transconductance of 1740 mS/mm and an extrinsic current-gain cutoff frequency of 340 GHz at room temperature; the latter is the highest value yet reported for any three-thermal semiconductor device. We also report for the first time a detailed comparison of the small-signal characteristics of a pseudomorphic and a lattice-matched AlInAs/GaInAs HEMT with similar gate length (50 nm) and gate-to-channel separation (17.5 nm): the former demonstrates a 16% higher transconductance and a 15% higher current-gain cutoff frequency, but exhibits a 38% poorer output conductance. Finally, we offer an analysis on the high-field transport properties of ultra-short gate-length AlInAs/GaInAs HEMT's. This analysis shows that a reduction of gate length from 150 to 50 nm neither enhances nor reduces their average velocity. In contrast, the addition of indium from 53% to 80% improves this parameter by 19%, from approximately 2.6 to 3.1 x 10(7) cm/s.