Optical quenching of the near-intrinsic photocurrent in semi-insulating bulk GaAs

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Abstract
The optical quenching of the photoresponse of GaAs when it is subject to a prolonged 1.15-eV optical excitation is one of the most important properties of the EL2 level in GaAs. Another quenching phenomenon takes place after excitation with photons in the same range, that is the optical quenching of the photoresponse in the near band-edge spectral region. Both quenching effects seem to be strongly correlated with changes in the configuration of the EL2 level, due to variations in the charge state of this level. In this way we can conceive a mechanism where EL2 captures electrostatically shallow levels when it is optically ionized at low temperature. By photoconductivity studies, we have seen that capture of shallow levels is accomplished after EL2 has relaxed to a metastable state EL2* which could be described on the basis of a mechanism similar to that recently proposed by M. Levinson.