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 topography, of the laser degradation due to the formation of misfit dislocations. We drive the laser diode under a high-energy, high-flux synchrotron micro-x-ray beam. We simultaneously obtain both the laser characteristic curve and the structural characteristics during operation, i.e. the presence of mifit dislocations, laser diode curvature and strain status. From the strain we measure the temperature increase in the epilayer due to the injection current. In other lasers device degradation occured without the formation of misfit dislocations, but by mass transport, and in other lasers no structural degradation was observed.