Observation of dislocation generation in highly strained quantum well lasers during operation

For the first time, we have obtained the real-time observation, by x-ray to pography, of the laser degradation due to the formation of misfit dislocati ons. We drive the laser diode under a high-energy, high-flux synchrotron mi cro-x-ray beam. We simultaneously obtain both the laser characteristic curv e and the structural characteristics during operation, i.e. the presence of misfit dislocations, laser diode curvature and strain status. From the str ain we measure the temperature increase in the epilayer due to the injectio n current. In other lasers device degradation occurred without the formatio n of misfit dislocations, but by mass transport, and in other lasers no str uctural degradation was observed.