Degradation mechanism limiting the lifetime of ZnSe-based white light-emitting diodes

The degradation mechanism responsible for limiting the lifetime of ZnSe-based white light-emitting diodes was studied. A systematic investigation on the effects of pre-existing stacking faults and threading dislocations, along with point defects in the epitaxial layers was conducted by monitoring their behavior during an aging experiment. Our experimental results, in conjunction with numerical calculations performed on degraded device structures, suggest that the deterioration of the internal quantum efficiency owing to the reduction of the net acceptor concentration in the p-ZnMgSSe cladding layer is responsible for the decline of the optical output power. The reduction in the free hole concentration has an effect of increasing the electron leakage current, leading to a decrease in the carrier injection efficiency. It is also proposed that the carrier depletion effect in the p-cladding layer is due to self-compensation resulting from the increase in the concentration of N-related deep donors.