Reduction of the effects of InGaAs alloy disorder by using superlattices as the conduction channel in modulation-doped heterostructures
We present the photo-Hall electrical properties of MBE-grown modulation-doped field-effect transistors (MODFET) structures using the so-called short-period superlattices (SPS) channel of InAs and GaAs instead of the standard InGaAs alloy channel. Photo-Hall measurements present the advantage of permitting the observation of mobility versus carrier density curves so that the effect of the replacement by the SPS channel can be better understood. The variables were the indium content (y=0.08 or 0.25) and the channel thickness (80 Angstrom or 125 Angstrom), and the approach was to compare the results for the two structures. Our results indicate that for y=0.08, the electrical properties are the same for both samples, either for using the SPS or the alloy channel. On the other hand, the electrical properties differ significantly for an indium content of y=0.25. Our conclusion is that the scattering associated with the alloy disorder increases with the indium content and that this deleterious effect can be reduced by replacing the alloy channel by a SPS channel.