We report on the properties of GaAs/AlGaAs multiple quantum wells grown at medium temperature range 300-400 degreesC. The samples exhibit both of sharp exciton absorption and ultrafast carrier lifetime, which are suitable as photorefractive devices. Photoluminescence, absorption spectroscopy, optical transient current spectroscopy and pump-probe technique were used to characterize the materials grown on GaAs (0 0 1) on-axis or miscut substrates. Using a YAG:Nd laser as a pump source, the quenchable characteristics of EL2-like defects were observed in electroabsorption for the first rime. By optimizing growth parameters and device structure, the transient diffraction efficiency approaches 1.2% and 4.5% in non-degeneration four-wave mixing under Frantz-Keldysh and Stark geometry, respectively.