The carrier localization and the inhibition of carrier transport along the growth axis (vertical transport) are studied by means of photoluminescence experiments performed at 1.7 K in purposely disordered GaAs/GaAlAs superlattices. When the well widths are randomly varied, minibands of extended states shrink and localized states are created in their tails. Consequently the vertical transport efficiency decreases and sharply vanishes when disorder induces fluctuations of the eigenenergies which are comparable to half of the unperturbed superlattice bandwidth. By an increase of temperature the vertical transport becomes thermally activated.

• Received 27 May 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.1464