Role of excited states in Shockley-Read-Hall recombination in wide-band-gap semiconductors

Defect-assisted nonradiative Shockley-Read-Hall recombination is an important process in wide-band-gap semiconductors. However, nonradiative capture rates decrease exponentially with the energy of the transition, and therefore the mechanisms by which such recombination can take place are unclear. The authors show here that excited states of defects play a key role in turning specific defects into efficient nonradiative centers. The wider the band gap of the material, the greater a role these excited states are likely to play. Specifically, the authors can explain why certain gallium vacancy complexes are efficient nonradiative centers in group-III nitrides, the key materials for solid-state lighting.