Operation-induced degradation of GaP light-emitting diodes

After GaP red light-emitting diodes (LED's) had been degraded by the forward-biased operation, changes of the light output, the minority carrier lifetime, the photocurrent, and the photocapacitance were measured. There was a linear decreasing relation between the light output and the carrier lifetime. A center which was related to the degradation of the light output was observed by means of photocurrent and photocapacitance measurements. This center's energy level is about 0.8 eV from either the valence or conduction band. This center was observed to increase in concentration with degradation. However, the contribution of this center to the minority carrier lifetime is not established since the capture cross sections of the center are unknown and is not known whether the center occurs on the n-side, or the p-side, or on both sides. This center does not appear to be an oxygen donor.