PSEUDOMORPHIC ALGAAS/INGAAS SQW-MODFETS WITH DOUBLE-SIDED MODULATION DOPING

Pseudomorphic Al0.23GaO.77As/InxGa1-xAs/Al0.23Ga0.77As QW-structures with double sided modulation doping have high 2DEG-densities between 1.5-10(12) 2.8-10(12) cm(-2) for In-contents 0 less than or equal to x less than or equal to 0.3. MODFETs with T-shaped 1.5 1012 cm gates (L(G) = 0.19 mu m) were fabricated by e-beam lithography and a selective RIE gate recess yielding threshold voltage variations of 20 mV. The transit frequency f(T) = 93 GHz is remarkably high for the AlGaAs/GaAs-devices and rises to 109 GHz for x = 0.25. At 12 GHz the latter devices exhibit a minimum noise figure F-min = 0.54 dB and an associated gain G(ass) = 15 dB. Within 0.15 less than or equal to x less than or equal to 0.3 DC- and RF-data remain essentially unchanged.