The migration of gold from the p-contact as a source of dark spot defects in InP/InGaAsP LED's

In this paper, the formation of dark spot defects (DSD's) in InP/InGaAsP LED's is studied by cathodoluminescence (CL) imaging, electron-beam-induced-current (EBIC) imaging, Auger electron spectroscopy (AES), and energy dispersive X-ray spectroscopy (EDS). Defects resulting in DSD's are shown by CL and EBIC to be located in either the p-InGaAsP contact layer or the p-InP confining layer for short aging times. For longer aging times, these defects are also found in 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 size inclusions at the contact layer-confining layer interface of cylindrically-lapped wafers using AES and 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.