Picosecond laser pulses were used to simulate current injection and generate dark defects in ZnSSe/ZnCdSe quantum well structures. The formation of the defects was monitoredinsituwith a photoluminescence microscope setup, with spatial resolution of about 1 &mgr;m. Dark defects are observed to form in the ZnCdSe quantum well, analogous to electrical injection in separate confinement heterostructure diode lasers. Transmission electron microscopy of the optically generated dislocation network gives further insight to the origin of the defect microstructure. ©1995 American Institute of Physics.