Long lived, lifetested GaAlAs/GaAs stripe geometry, double heterostructure lasers have been examined in the scanning electron microscope using a combination of cathodoluminescence, electron beam induced conductivity, and electron probe microanalysis. The dark spot arrays, occasionally seen in the cathodoluminescence images of the active layers of these devices, have been found to be caused by the diffusion of copper into the laser chip from the heat sinks, despite the presence of a nickel barrier layer on the heat sinks.