In this paper, the discoloration of indium-gallium-nitride (InGaN) on sapphire (Al2O3) substrate after processing in electron beam vacuum evaporation for mirror metal evaporation has been investigated. Discoloration can be detrimental to light output of a light emitting diode (LED) as the light extraction through discolored gallium nitride (GaN) epitaxy is impacted. The investigation shows that the discoloration caused by an interaction between few factors such as the level of organic contamination present at the edges of the substrate, contact area with holding dome of the evaporator, thickness of the film deposited and radiation intensity from the evaporation source. Reflection Spectroscopy was used to quantify reflectivity of discolored mirror metal while X-ray fluorescence spectrometry (XRF) was used to measure film thickness and time of flight – secondary ion mass spectrometry (TOF-SIMS) was employed to measure organic contamination amounts. A residual gas analyzing (RGA) technique was established to detect potential discoloration to eliminate disruptions to manufacturing.
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