Lateral Scale Down of InGaAs/InAs Composite-Channel HEMTs With Tungsten-Based Tiered Ohmic Structure for 2-S/mm and 500-GHz

A laterally scaled-down ohmic structure and an InGaAs/InAs composite channel improve the dc and RF characteristics of InP-based HEMTs. We reduced the distance between the gate and ohmic metal to less than 100 nm and to form sub-100-nm-long gate simultaneously, and also introduced device passivation for future construction of subterahertz-band integrated circuits. A 50-nm-gate HEMT exhibiting extrinsic transconductance of 2.0 S/mm and extrinsic current gain cutoff frequency (fT) of 496 GHz was successfully fabricated with this technology. This is the first report of a transistor with both 500-GHz-class fTand large current drivability