Persistent photoconductivity has been observed at low temperatures inthin,unintentionallydopedGaInP/GaAs/GaInP quantum wells. The two‐dimensional electron gas was studied by low field Hall and Shubnikov–de Haas effects. After illumination with red light, the electron concentration increased from low 1011cm−2to more than 7×1011cm−2resulting in an enhancement of both the carrier mobility and the quantum lifetime. The persistent photocarriers cannot be produced by DX‐like defects since the shallow dopant concentration in the GaInP layers is too low to produce the observed concentration. We suggest that the persistent carriers are produced by photoionization of deep intrinsic donors in the GaInP barrier layer. We also report observation of a parallel conduction path in GaInP induced by extended illumination. ©1995 American Institute of Physics.