Optical and structural analysis of degraded high power InGaAlAs/AlGaAs lasers

The failure of high power InGaAlAs:AlGaAs double quantum well (DQW) lasers has been studied by plan-view photoluminescence (PL), cross sectional (002) dark field TEM and X-ray microanalysis. The lasers were operated at elevated driving currents beyond rollover in order to stimulate and analyse degradation processes encountered during accelerated lifetime testing. The damage consists of elliptical areas within which the original DQW structure was destroyed due to outdiffusion of Al into the confinement layers. The damaged areas started from the output mirror indicating that the device temperature was somewhat higher near the facet. The Ga vacancies governing the Al diffusion were likely produced by a mechanism of recombination enhanced defect reaction (REDR). The dislocations always present in the damaged areas are expected to be generated by the point defects produced by REDR as well as by localized thermal stresses.