Abstract
In p‐modulation‐doped quantum wells of GaAs/AlGaAs extremely high negative photoconductivity is observed at low temperatures. The in‐plane sheet resistance can be increased by a factor of more than 60 with illumination of less than 1 W/cm2. Spectral analysis shows that the effect is mainly due to hole trapping in the potential minima of AlGaAs and subsequent recombination of minority electrons.