Temperature enhancement of the photorefractive effect in GaAs due to the metastable state of theEL2 defect

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Abstract
We present a theoretical and experimental analysis of photorefractive two-beam coupling in undoped GaAs as a function of temperature. The theoretical treatment includes the metastable state of the EL2 defect with its optical properties (optical generation and optical recovery) in the photorefractive model. Three major features are predicted by this model: First, a change of the sign of the photorefractive beam coupling gain around 150 K; second, an enhancement of the space-charge field by a factor of 2 compared to the diffusion field; and, finally, the appearance of a strong peak due to an absorption grating around 150 K. All these features are actually observed experimentally with a good correlation between experimental data and theoretical simulation.