The features present in the capacitance– and conductance–voltage characteristics of [100]‐ and [111]‐oriented InGaAs/GaAs multi‐quantum well (MQW)p‐i‐nstructures under illumination are described. Sequential tunneling of electrons and holes is proposed to explain the different peaks observed, as they occur at voltages corresponding to resonant alignment of energy levels of adjacent wells. Two kinds of piezoelectric [111] devices are analyzed, with positive or negative average electric fields in the MQW region. The voltage corresponding to zero average electric field in the MQW is detected by a feature in the dark device capacitance. For the sample with negative average electric field, the capacitance characteristics clearly reflect the presence and evolution with voltage of a long range screening of the piezoelectric fields by the photogenerated carriers. ©1995 American Institute of Physics.