Observation of Superlattice Effects on the Electronic Bands of Multilayer Heterostructures

Electroreflectance measurements have been performed on the GaAs-${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ superlattice, and the observed structure has been related to interband transitions at different points of the Brillouin zone. For increasing $x$ the energies of these transitions shift progressively to higher values with respect to those of bulk GaAs, indicating the effect of the superlattice potential on the band structure beyond the zone center. In contrast, similar shifts observed in ${\mathrm{In}}_{1-x}{\mathrm{Ga}}_x\mathrm{As}-\mathrm{Ga}{\mathrm{Sb}}_{1-y}{\mathrm{As}}_y$ only occur for $x$,$y>\mathrm{}0.2\mathrm{}$, an anomaly arising from its unusual periodic potential.