We have investigated the electronic properties of an ${\mathrm{In}}_{0.15}$${\mathrm{Ga}}_{0.85}$As-GaAs strained-layer superlattice using photoluminescence excitation and photocurrent spectroscopies. Flatband spectra show transitions at the center and edge of the Brillouin minizone, and photocurrent spectra at finite bias show, for the first time in this system, the effects of Wannier-Stark quantization. The heavy-hole transitions evidence the importance of the excitonic interaction between spatially separated carriers. The light-hole transitions show a qualitatively different behavior resulting from their weak confinement in the GaAs layers. Our data agree with a numerical calculation of the electro-optical absorption spectra.

• Received 15 December 1989

DOI:https://doi.org/10.1103/PhysRevB.41.8568