Abstract
Spectroscopic emission microscopy and cathodoluminescence have been applied to analyze the mechanism causing light output degradation in AlGaAs infrared light emitting diodes (LEDs). Using a spectroscopic emission microscope which was put together in-house, the emission properties of the AlGaAs LEDs under forward bias were analyzed before and after device decapsulation. Monochromatic cathodoluminescence (CL) microscopy was used to further analyze the near-surface AlGaAs epitaxial layer. Since the information provided by the cathodoluminescence method is limited by the penetration depth of the incident electrons, the emission images are useful in revealing information that is close to the pn junction. This is especially so for deep junctions which are very difficult to assess using an electron probe. Crystalline defects at and in the vicinity of the junction, and defects near the surface can be separated using a combination of emission microscopy and cathodoluminescence techniques. The emission microscope, equipped with both spectroscopic and imaging capabilities, has found applications in the study of the emission properties of light emitters.