Results on semi-insulating photorefractive multiple quantum well (MQW) devices operating without trapping layers are reported. The device structure consists of a MQW doped with Fe(1017 cm−3)isolated from the doped contact by intrinsic standoff layers. The photocarriers generated by the pump pulse are trapped in the MQW and screen the applied electric field in the MQW. Output diffraction efficiency of 0.2&percent; is measured in a nondegenerate four-wave-mixing configuration and the rise time of the diffraction signal reaches 200 ns. ©1997 American Institute of Physics.