Design, fabrication, and characterization of ultra high speed AlGaAs/InGaAs MODFETs

The authors report the design, fabrication, and characterization of ultra-high-speed 0.15- mu m mushroom gate Al/sub 0.30/Ga/sub 0.70/As/In/sub 0.25/Ga/sub 0.75/As modulation-doped field-effect transistors (MODFETs) with current gain cutoff frequency (f/sub T/) over 150 GHz. It is demonstrated that with proper device design and fabrication techniques, the switching speed of the AlGaAs/InGaAs (on GaAs) MODFET approaches that of the best AlInAs/InGaAs (lattice matched to InP) devices (f/sub T/=165 GHz at 0.1- mu m gate length). The devices reported here typically exhibit a maximum current density of 630 mA/mm, peak transconductance of 650 mS/mm, peak f/sub T/ of 152 GHz, and best power-gain cutoff frequency in excess of 200 GHz. >