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The optoelectronic properties of undoped type-II GaAs0.7Sb0.3/GaAs (100) multiple quantum wells have been investigated by photoluminescence (PL), and photoconductivity measurements. Quite interestingly, persistent photoconductivity (PPC) has been discovered in this material. The decay kinetics of the PPC effect can be well described by the stretched-exponential function IPPC(t)=IPPC(0)exp[-(t/τ)β], (0<β<1), which is similar to the behavior observed in many disorder systems. Through the study of the PPC effect under various conditions, and combining with the characteristics of the PL spectra, we identify that the origin of the PPC effect arises from the spatial separation of photoexcited electrons and holes. Here, the photoexcited electrons fall into the GaAs layer, and holes are trapped by local potential minima due to alloy fluctuations in the GaAsSb layer. This process prevents the recombination of electrons and holes, and thus the PPC occurs. In order to return to the initial states, photoexcited electrons have to overcome the energy barrier caused by the conduction band offset. [ABSTRACT FROM AUTHOR]

Anisotropic property of type-II GaAs/GaAsSb heterostructures was studied by photoluminescence (PL) and photoconductivity (PC). It was found that the PL and PC spectra exhibit a strong in-plane polarization with respect to 〈011〉 axis with polarization degrees up to 40%. We showed that the polarization does not depend on the excitation intensity as well as temperature, which excludes any extrinsic mechanisms related to the in-plane anisotropy. The observed polarized optical properties of GaAsSb/GaAs multiple quantum wells was attributed to the intrinsic property of the orientation of chemical bonds at heterointerfaces. [ABSTRACT FROM AUTHOR]