Investigation of degradation in homoepitaxially grown ZnCdSe/ZnSe light emitting diode

From the transmission electron microscope (TEM) observation of ZnSe homoepitaxial films, it is clarified that the major pre-existing defects in the film are Shockley extended dislocations. Correlation between the etch pits and the Shockley extended dislocations are also confirmed. The degradation mode of a ZnCdSe/ZnSe homoepitaxial light emitting diode (LED) is discussed on the basis of the microscopic observation. Many dark spot defects (DSDs) are observed in the emission pattern just after turn-on, and they enlarge and become pronounced keeping their round shape. The growth velocity of the DSD is less than 0.056 mu m/min for the current density of 408 A/cm(2). The DSD density is almost the same as the etch pit density (EPD) of the as-grown LED wafer.