Evidence that the 0.635-eV luminescence band in semi-insulating GaAs is not EL2 related

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Abstract
By utilizing the quenching effect of the deep EL2 defect in semi-insulating GaAs in different optical measurements, it has been possible to show that the 0.635-eV photoluminescence band is not related to EL2. The previously observed ‘‘EL2 behavior’’ of this luminescence band is shown to be only an indirect effect where the EL2 level acts as an intermediate step in the excitation process. Evidence is also given that the sharp below-band-gap photoluminescence excitation peak (1.50 eV) which has been regarded as an EL2 feature is actually not related to EL2. A new photoluminescence excitation band with a threshold at ∼1.1 eV is also observed.