Barrier localization effects in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-${\mathrm{Al}}_{\mathit{y}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{y}}$As superlattices

We demonstrate that the recently observed phenomenon of barrier localization in magnetic II-VI superlattices is also present in III-V superlattices. We investigate the role of subsidiary minima and show that above-barrier localization in both the Γ and X barriers occurs for type-I and type-II (001) superlattices in the ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-${\mathrm{Al}}_{\mathit{y}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{y}}$As system. In addition, explicit evaluation of the oscillator strengths shows that the interband transitions involving the X-like conduction-band above-barrier states remain weak even though these are spatially direct.