Miniband dispersion in GaAs/AlxGa1−xAs superlattices with wide wells and very thin barriers

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Abstract
Photoreflectance spectra have been used to characterize miniband formation in GaAs/ Alx Ga1−x As superlattices with wide wells (275–255 Å) and withb arriers as thin as 17 Å. Thirty‐two optical transitions are resolved in the photoreflectance spectra of the 17 Å barrier sample. These experimental transitions match all those theoretically predicted from the selection rule Δn=0, including Γ‐ and Π‐type transitions arising from miniband dispersion; these results imply sample perfection. A sample with a 40 Å barrier exhibits forbidden transitions with Δn≠0; these additional transitions, together with the narrow width of the minibands for 40 Å barriers, create difficulty in resolving the miniband structure.