DC and microwave performance of submicrometer InGaAs HIGFETs

The DC and microwave performance of InAlAs/InGaAs/InP heterostructure insulated-gate FETs (HIGFETs) with gate lengths down to 0.3 mu m is reported. A non-recessed-gate process with refractory airbridge gates and self-aligned contact implants was used to assure minimum threshold variation, minimum parasitic resistance, and minimum gate leakage current. These devices offer improved threshold uniformity while preserving the high-speed characteristic of In/sub 0.53/Ga/sub 0.47/As channels. An average of eight HIGFETs with 1.1- mu m gate length showed peak DC transconductance of 456+or-5 mS/mm and on-state resistance of 1.14+or-0.02 Omega -mm. The output conductance was relatively high, about 60 mS/mm without wide-bandgap buffers. Full S-parameter measurements from 0.5 to 25.5 GHz were used to determine the unity-current-gain frequency, f/sub t/=28 GHz, and the unity-power-gain frequency, f/sub mag/=27 GHz. HIGFETs with 0.6- mu m gate length showed improved DC and RF performance, with peak transconductance of 528+or-3 mS/mm, on-state resistance of 0.84+or-0.2 Omega -mm, f/sub t/=45 GHz, and f/sub mag/=36 GHz. Some short-channel effect is evident in the output conductance. HIGFETs with 0.3- mu m gate length showed severe short-channel effect. With the addition of a wide-bandgap buffer layer and adjustments to the implant process, control of the short-channel effect at smaller gate lengths should be practical.<
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