Reliability and wearout characterisation of LEDs

LEDs play a key role as an active element in electronic circuitry – for example in optocouplers. Their life time strongly depends on the operation conditions. Degradation usually starts by the generation of both reverse and forward bias direction pinpoint leakage paths. When the resistance of such a path becomes lower than the regular operational resistance in forward direction, it will start to act as a bypass. Then, reduced and inhomogeneous emission is the first degradation indicator. The paper describes degradation mechanisms and their characterisation.