Miyazawa et al. [Appl. Phys. Lett. 43, 853 (1983)] have recently established a spatial correlation between variations in field-effect transistor performance and nonuniformities in the cathodoluminescence (CL) efficiency of semi-insulating (SI) GaAs substrates. In this study, we compare the CL uniformity of both Cr-doped and undoped SI GaAs crystals grown by the liquid-encapsulated Czochralski (LEC) technique with undoped SI crystals grown by the horizontal gradient freeze (HGF) technique. In contrast to the LEC crystals, HGF GaAs has extremely uniform CL characteristics which should result in uniform device performance.
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.
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