High conductance in random superlattices with correlated disorder

Abstract

We study d.c. conductance of disordered GaAs-Gal_xAl,As superlattices where the disorder is intentional and short-range correlated. We consider Gal _, Al,As layers of the same thickness, where GaAs layers present two different thicknesses randomly distributed along the growth direction, with the constraint that one of them always appears in pairs. A set of almost unscattered electron states is observed in spite of the disorder, revealing itself through a distinct conductance maximum. Interestingly, this maximum is also detected in imperfect superlattices, where interface roughness is taken into account by allowing Quantum-well thicknesses to fluctuate around their nominal values. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization effects of disorder, even in the presence of imperfections.