Cathodoluminescence evaluation of dark spot defects in InP/InGaAsP light-emitting diodes

In this study, the formation of dark spot defects (DSD’s) in InP/InGaAsP light-emitting diodes (LED’s) is evaluated by cathodoluminescence imaging and energy dispersive x-ray spectroscopy (EDS). Defects resulting in DSD’s are shown to be located in either the p-InGaAsP contact layer, the p-InP confining layer, or the InGaAsP active layer. The presence of gold was not detected at the DSD’s using EDS. However, gold was found in the form of submicron-sized inclusions in the contact layer and confining layer of cylindrically lapped wafers using EDS. Our results strongly suggest that the migration of gold from the p contact during device processing and aging results in the formation of DSD’s in InP/InGaAsP LED’s.