Degradation of GaAs0.9P0.1 light-emitting diodes for optical fiber communication with internal stress

Abstract

Degradation mechanisms of GaAs0.9P0.1 light-emitting diodes for optical fiber communication systems were studied to elucidate the effects of internal compressive stress (on the order of 107–108 dyn/cm2) on initial rapid degradation. The diodes were fabricated from wafers with various phosphorus composition gradients (?0.7%/μm) in the tapered layer.Experimental results from the degradation of the diodes operating at 660 A/cm2 showed that the lifetimes of the diodes increased with decreasing the compositional grading in the crystals. The improved lifetime is due not only to the suppression of 〈110〉 dark-line defects but also to the slow growth velocities of 〈100〉 dark-line defects and due to slow accumulation rates of nonradiative recombination centers near the PN junctions at low internal stress. For the first time, the growth velocities of 〈100〉 dark-line defects during initial rapid degradation were observed to depend on the internal compressive stress.