HIGHER MOBILITY OF CHARGE-CARRIERS IN INAS GAAS SUPERLATTICES THROUGHTHE ELIMINATION OF INGAAS ALLOY DISORDERS ON GAAS/

In this work, we present the Hall electrical properties for molecular beam epitaxy,grown modulation-doped field-effect transistors structure s using a short-period superlattices channel of (InAs)(1.1+/-0.1) (GaA s)(n) where the indexes 1.1 and n represent the number of InAs and GaA s monolayers, respectively These properties are compared with those of structures using the alloy in the channel and the variables were the indium content (y=0.08+/-0.01-0.25+/-0.01) and the channel thickness ( 80-150 Angstrom). The mobility and the free carrier concentration were obtained as a function of the illumination intensity of a light-emitt ing diode at 77 K. Our results indicate that for indium content around y=0.08+/-0.01, the electrical properties are independent of using sho rt-period superlattices or alloy channels: For an indium content aroun d y=0.25+/-0.01 the electrical properties change significantly for the two structures. For the same carrier concentration (n=2.8x10(12) cm(- 2)), we observed for the sample having the short-period superlattices structure mobilities 33% higher than those for the alloy structure. Ou r conclusion is that the scattering associated with the alloy disorder increases with the indium content and that this deleterious effect ca n be reduced, replacing the alloy layer with short-period superlattice s. (C) 1995 American Vacuum Society.