Charge Transport in High-Resistivity Photorefractive Crystals (Bi12SiO20, ZnSe, GaAs)

The paper reviews our studies[1−7] concerned of photoinduced charge dynamics and electric field evolution in the case of external field screening. The experimental methods providing possibility of electric field distribution direct measurements are considered. It is found that there are two different regimes of electric field screening which depend on experimental conditions (kind of crystal, temperature): narrowing of major cariers depletion region and stratification effect (numerous space charge layers of alternating sign) with increasing charge density - regime 1 and the slow broadening of single layer with constant charge density may occur in bulk of a sample - regime 2.These regimes were experimentally investigated in Bi12SiO20, ZnSe and GaAs crystals. A theoretical description is given of a sufficiently general charge transfer model involving the photogeneration of free carriers, their drift and trapping throughout the depth of the material.