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.