0.2- mu m gate-length atomic-planar doped pseudomorphic Al/sub 0.3/Ga/sub 0.7/As/In/sub 0.25/Ga/sub 0.75/As MODFETs with f/sub T/ over 120 GHz

The authors report the DC and RF performance of nominally 0.2- mu m-gate length atomic-planar doped pseudomorphic Al/sub 0.3/Ga/sub 0.7/As/In/sub 0.25/Ga/sub 0.75/As modulation-doped field-effect transistors (MODFETs) with f/sub T/ over 120 GHz. The devices exhibit a maximum two-dimensional electron gas (2 DEG) sheet density of 2.4*10/sup 12/ cm/sup -2/, peak transconductance g/sub m/ of 530-570 mS/mm. maximum current density of 500-550 mA/mm, and peak current-gain cutoff frequency f/sub T/ of 110-122 GHz. These results are claimed to be among the best ever reported for pseudomorphic AlGaAs/InGaAs MODFETs and are attributed to the high 2 DEG sheet density, rather than an enhanced saturation velocity, in the In/sub 0.25/Ga/sub 0.75/As channel.<
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