Transient band bending in a staggered-alignment type-II multiple-quantum-well structure

We observed a critical change of luminescence spectra under high-density excitation in staggered-alignment type-II ${\mathrm{Al}}_{0.34}$ ${\mathrm{Ga}}_{0.66}$As-AlAs multiple quantum wells. Under the same density excitation (∼10 μJ ${\mathrm{cm}}^{\mathrm{-}2}$), a redshift of the Γ-Γ luminescence and saturation of the X-Γ luminescence were observed. Simultaneously, a blueshift of the X-Γ luminescence was observed in the time-resolved spectrum. These phenomena show the carrier-induced transient band bending caused by real-space charge transfer through the interface.