Universal curves for optical power degradation of II–VI light-emitting diodes

Abstract

We propose a transient recombination-enhanced defect-generation model to analyze the degradation of optical output powers of blue-green II–VI light-emitting diodes (LEDs). We find an analytical solution and discover a set of universal curves for the time dependence of optical output power, which agree very well with the experimental data for strained CdZnSe quantum-well structures. Our model shows that the optical power can be non-exponential in character and its long-time behavior has a 1/t dependence. This 1/t dependence is also related to the growth of the defect density, which should behave as a t1/2 dependence. The generation of new defects due to electron-hole recombination at the defect sites is found to be the dominant degradation mechanism for II–VI LEDs.