Limitation to Shockley–Read–Hall model due to direct photoionization of the defect states

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Abstract
Restrictions on the standard Shockley–Read–Hall (SRH) model in the recombination processes due to direct photoionization of the trapping centers have been theoretically studied. We find that, for photon energies even slightly in excess of the energy gap (i.e., ℏω≥Eg+0.01 eV) photoionization via defect states may normally be neglected in comparison with interband photogeneration, even in indirect semiconductors (e.g., n‐type silicon doped with gold). For photon energies below Eg, the recombination expressions for SRH are found to be simply replaced by similar expressions with suitably defined effective values n*1 and p*1, which incorporate the photoionization of the trapping centers.