Electric-field-induced combination of Wannier-Stark localization and type-I-type-II crossover in a marginal type-I GaAs/AlAs superlattice

We have investigated the influence of carrier transport on photoluminescenc e (PL) properties in a marginal type-I GaAs/A1As superlattice whose lowest X state (X-1) is situated in the lowest Gamma (Gamma(1)) miniband. By apply ing a bias voltage, the PL signal from the lower edge of the Gamma(1) minib and disappears, while Stark ladder PL is observed from the X-1 state. With a further increase of the bias voltage, the PL signal from the X state disa ppears, while the PL signal from the Gamma(1) state reappears as a Stark la dder transition. To confirm the electric-held dependence of the Gamma(1)- a nd X-1-related transition energies observed in the PL spectra, the correspo nding electroreflectance spectra have been also measured. This PL property can be attributed to competitive carrier transport among the Gamma miniband , the localized Gamma Stark ladder states, and the X-1 state, which results in the transition between type-I and type-II radiative recombination proce sses.