PN junctions and diodes
How does an LED emit light?
- AElectrons and holes injected under forward bias emit light when they recombine
- BIt is heated by reverse breakdown current and glows by thermal radiation
- CCurrent flows when light falls on it
Show answer and explanation
Answer: A. Electrons and holes injected under forward bias emit light when they recombine
When forward voltage is applied to an LED, electrons are injected from the n side and holes from the p side into the junction, and when they recombine they release energy corresponding to the band gap as light. Current flowing when light falls on the device is how a photodiode works.