Mechanism of catastrophic degradation in InGaAsP/InP double-heterostructure light emitting diodes with Ti/Pt/Au electrodes

Abstract

The mechanism of catastrophic degradation of InGaAsP/InP double-heterostructure light emitting diodes with Ti/Pt/Au electrodes through the application of pulsed large current, is investigated by electroluminescence topography, scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy. As the degradation is promoted, a dark region is generated in the center of the light emitting area. This then develops through the whole light emitting area. During the generation and the development process of the dark region, no dislocations are generated. The dark region, which develops through the whole light emitting area, consists of amorphous area and nonstructural small grains. There is clear compositional inhomogeneity in the region corresponding to the dark region. However, the electrode metals are not detected. The mechanism of the catastrophic degradation can be explained by local heating at the contact region by large current pulses, melting of the matrix crystal at the current above the degradation current level, and development of the molten region through the whole light emitting area.