Homogeneous degradation of surface emitting type InGaAsP/InP light emitting diodes

The homogeneous degradation modes of InGaAsP/InP light-emitting diodes (LED) with either a Au-Zn ohmic type or a Ti/Pt/Au Schottky type p-side electrode are discussed. In LEDs with a Au-Zn electrode homogeneous degradation goes through two distinct stages: an initial period of very slowly decreasing optical output power followed by a period of rapidly decreasing optical output power. Both modes are caused by electrode metal diffusion and alloy reactions between the electrode and the cap, cladding, and active layers during aging. In Ti/Pt/Au electrode LEDs homogeneous degradation is accompanied by a series resistance increase, which is caused by the formation of In- and Ga-depleting interfacial layers between the electrode and the cap layer. This study indicates that homogeneous degradation depends on the interface stability between the p-side electrode and the cap layer.>