Stress-related
- Thermal runaway Nonhomogenities in the substrate, causing localized loss of thermal conductivity, can cause thermal runaway where heat causes damage which causes more heat etc. Most common ones are voids caused by incomplete soldering, or by electromigration effects and Kirkendall voiding.
- Current crowding, non-homogenous distribution of the current density over the junction, formation of current filaments. This may lead to creation of localized hot spots, which poses risk of thermal runaway.
- Electrostatic discharge (ESD) may cause immediate failure of the semiconductor junction, a permanent shift of its parameters, or latent damage causing increased rate of degradation. LEDs and lasers grown on sapphire substrate (see silicon on sapphire) are more susceptible to ESD damage.
- Reverse bias Although the LED is based on a diode junction and is nominally a rectifier, the reverse-breakdown mode for some types can occur at very low voltages and essentially any excess reverse bias causes immediate degradation, and may lead to vastly accelerated failure. 5V is a typical, "maximum reverse bias voltage" figure for ordinary LEDs; some special types may have lower limits.
- Catastrophic optical damage, occurring in high power semiconductor lasers
Read more about this topic: List Of LED Failure Modes