Degradation sources in GaAs-AlGaAs double-heterostructure lasers

Several sources of the dark-line defect (DLD) that causes rapid degradation of GaAs-AlGaAs double-heterostructure (DH) lasers have been identified by means of photoluminescence (PL) topography and a laser-induced degradation technique. All the sources that have been identified correspond to crystal defects, among which dark-spot defects (DSD) that are native to as-grown wafers are found to be most important. The growth and propagation processes of DLD´s and DSD´s have also been investigated. These defects are found to be highly mobile under high-intensity laser pumping. The correlation between the substrate dislocations and the DSD´s has been examined by etching and X-ray topography. Although most DSD´s correspond to etch-pits in epilayers, they are not always correlated with substrate dislocations.