The physics of GaN-based light-emitting diodes

The past three decades have witnessed substantial progress in the performance of GaN-based light-emitting diodes. GaN light-emitting diodes, combined with wavelength-converting materials, enable highly efficient white-light sources that have caused a revolution in lighting applications, reaching more than 50% market adoption in the USA. This Review article discusses the underlying physics of GaN-based light-emitting diodes, focusing on how the quantum efficiency of the active region is affected by three key physical effects: intrinsic polarization fields, carrier localization by random alloy disorder, and crystal defects. Early theories are critically reviewed in view of current understanding and checked against the behaviour of real-world devices. We also offer perspectives on the prospects of extending III-nitride light emitters towards extreme wavelengths, at the ultraviolet and red ends of the spectrum.