Photo response of the EL2 absorption band and of the As+Ga ESR signal in GaAs

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Abstract
The photo response of the EL2 absorption band and of the As+ Ga ESR signal in GaAs is described and compared with the basic optical properties of the EL2 mid-gap level, as inferred from photocapacitance spectroscopy. Changes in the EL2 absorption band intensity induced by secondary below band-gap light are analysed and are explained in terms of the EL2 optical cross-sections known from photocapacitance studies. The thermal recovery of the EL2 absorption band following complete quenching is discussed. Below band-gap light can also induce changes in the GaAs absorption spectrum below 0.75 eV. They are attributed to optically induced persistent free carriers. Their generation is related to the presence of EL2. The photoresponse of the As+ Ga ESR signal in GaAs is reviewed. These results reveal that EL2 and AsGa have practically the same optical properties and provide the best evidence that EL2 and the As+Ga ESR are induced by the same defect