Crystal defects, such as dislocations, introduce electronic states into semiconductors and thereby degrade the desired electronic behavior of semiconductor devices. Special processing precautions are therefore pursued to minimize dislocation densities in semiconductor materials. When light irradiates a semiconductor, incident photons with appropriate wavelengths excite electrons and holes into traps such as point defects and dislocations. This modification of the population of charged defects can modify the flow stress required to propagate dislocations. This effect manifests itself as an inhibition of dislocation motion in type II‐VI compound semiconductors; whereas in type III‐V semiconductors light can enhance dislocation mobility. This effect is known as photoplasticity. In this article we report on the basic characteristics of photoplasticity in CdS and show how it can be exploited to reduce dislocation densities in semiconductor materials. ©1995 American Institute of Physics.