Role of excited states in Shockley-Read-Hall recombination in   wide-band-gap semiconductors
  Defect-assisted recombination is an important limitation on efficiency of optoelectronic devices. However, since nonradiative capture rates decrease exponentially with energy of the transition, the mechanisms by which such recombination can take place in wide-band-gap materials are unclear. Using electronic structure calculations we uncover the crucial role of electronic excited states in nonradiative recombination processes. The impact is elucidated with examples for the group-III nitrides, for which accumulating experimental evidence indicates that defect-assisted recombination limits efficiency. Our work provides new insights into the physics of nonradiative recombination, and the mechanisms are suggested to be ubiquitous in wide-band-gap semiconductors. 
Audrius Alkauskas, Cyrus E. Dreyer, John L. Lyons, Chris G. Van de   Walle
cond-mat.mtrl-sci