Theory of two species of electron-hole with shallow electron trap transport in photorefractive media

A new model of two species of electron-hole with shallow electron trap is presented. The model predicts that if the shallow trap accumulates large density of charge carriers, the photoconductivity can be a sublinear (or superlinear) function of light intensity, and the space-charge field increases (or decreases) and reaches a saturate value as intensity increases depending on the sign of dominant carrier. Comparison this model with previous ones shows that this model provides more common descriptions about photoconductivity and space-charge-field dependence of intensity.