Microstructural study of quantum well degradation in ZnSe-based laser diodes

The possibility to grow CdZnSSe quantum structures with a high structural quality is extremely important for light emitting devices in the blue-green spectral range. However, during device operation the degradation of the quantum well reduces the lifetime severely due to the formation of dark spot and dark line defects, which are not clearly understood. To investigate the mechanisms of defects formation degradation studies were performed for ZnSe-based laser diodes with quaternary CdZnSSe quantum well structures by means of electroluminescence, high-resolution X-ray diffraction and transmission electron microscopy. It was found that the degradation is closely connected to a blue shift of the emitted light and the formation of defects which are confined near to the quantum well. A partial broadening of the quantum well could be observed, which is attributed to the outdiffusion of Cd from the active region. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)