Categorizing light output degradation failures in LEDs using the relationship between defect revealing mechanisms responsible for electroluminescence (EL), cathodoluminescence (CL), EBIC, and reverse bias photoemission (RP)

This paper describes a methodology for the analysis of dark spot defects (DSDs) that accompany optical output intensity degradation (-/spl Delta/I/sub v/) in light emitting diodes (LEDs). There are many mechanisms that result in premature -/spl Delta/I/sub v/ failures. A methodology which has evolved from many years of failure analysis experience with LEDs allows -/spl Delta/I/sub v/ failures to first be separated into uniform or non-uniform degradation categories. Those with DSD symptoms can be further characterized utilizing the correspondence, or lack of it, between defect locations found by electroluminescence microscopy (EL), reverse bias photoemission microscopy (RP), electron beam induced current contrast imaging (EBIC), and cathodoluminescence imaging(CL). This approach has had good success in separating assembly and handling failures from faulty wafer fabrication and epitaxial growth failures. Using the location revealed by these techniques as a guide for cross section location, high resolution secondary electron imaging (SEI) or microchemical analysis, we have been successful in revealing the unique attributes at the defect location.