Chapter 6 Light-Emitting-Diode Reliability

Abstract

Publisher Summary The chapter focuses on light-emitting-diode (LED) reliability and deals with light-power and junction-temperature measurements in life testing. It presents the results of accelerated aging of InP-based LEDs and GaAs-based LEDs, including observed failure modes and estimates of mean time to failure (MTTF). Degradation in light output is the only important failure mode in lightwave LEDs. Most reports of reliability studies give only MTTF, and in most cases, this is much longer than any conceivable service life of a system. However, the suitability of an LED for a lightwave system must be assessed in terms of the failure rate or the cumulative number of expected failures that have to be replaced. To do this, it is necessary to know not only the MTTF but also the spread in the failure distribution and how effectively infant failures are removed by burn-in. The chapter discusses rapid degradation mechanisms in these devices with emphasis on the elimination of infant and freak failures. The most successful LED in terms of reliability has been the planar double-heterostructure (DH) structure. Infant failures in these structures can be effectively eliminated in a 100-hour burn-in. The chapter discusses possible long-term degradation mechanisms and considers reliability projections for GaAs-based LEDs.