A white LED based on II¯VI compound materials was developed. The optical output power and forward voltage of a typical ZnSe-based white LED lamp at a drive current of 20mA were 4.3mW and 2.6V, respectively. Device lifetime (half-time) at IF = 5mA have exceeded 2500h at 60C, corresponding to an estimated lifetime of over 20000h at 20C. The most important defects limiting the lifetime were the dislocations and the stacking faults penetrating the active layer. Origins of these defects were the dislocations in the substrate as well as lattice irregularities at the epilayer/substrate interface. Although no evidence had yet been found for microscopic defects in the cladding layers taking part in the degradation of white LEDs, its possibility cannot be neglected.

Effect of Defects on the Degradation of ZnSe-Based White LEDs. T.Shirakawa: Materials Science and Engineering B, 2002, 91-92, 470-5