A forward voltage (Vf) snapback phenomenon was observed during the analysis of silicon doped gallium-arsenide (GaAs) light emitting diodes (LEOs). In this paper emphasis is placed on both the techniques used during the analysis and the information obtained. Apart from the standard curve tracer characterizations, and utilization of two microsection techniques, significance is placed on the use of a laser scanning microscope (LSM). The LSM has four main analys is features: photoemission (FE) microscopy, optical beam induced current (OBIC), confocal microscopy and infrared laser scanning microscopy [1]. The analysis of the LEOs utilizes two of these features, PE microscopy and OBlC analysis. These techniques are used in a complementary fashion to analyze the forward voltage snapback. The analysis reveals two independent wafer processing related issues, a junction anomaly and an unintentional phantom junction at the substrate to epi interface. Both phenomena can result in the LED Vf snapback.

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