We have performed electroreflectance measurements on a five-period ${\mathrm{In}}_{0.24}$${\mathrm{Ga}}_{0.76}$As(3 nm)/GaAs(10 nm) strained-layer superlattice as a function of electric field. The applied electric field was exactly determined by the Franz-Keldysh oscillation of GaAs. We have resolved transitions between electrons confined in the ${\mathrm{In}}_{0.24}$${\mathrm{Ga}}_{0.76}$As layer and light holes localized in the adjacent layers. The type-II Stark-ladder transitions are clearly observed. The observed field evolution of the transition energy shows a nonlinear behavior originating from an anticrossing by coupling resonantly between the first light-hole subband and unconfined energy states of light holes.

• Received 24 January 1994

DOI:https://doi.org/10.1103/PhysRevB.50.2420