While researching LED failure modes, I came across a 2002 U.S. Department of Energy report outlining the viability of using light-emitting diodes for general illumination. This 112 page report covers many aspects of the physics behind LEDs as well as illumination profiles and manufacturing methods. This is kind-of a report on everything you wanted to know about LEDs but were afraid to ask. Unfortunately, it does not really cover LED failure modes.