Abstract-Semiconductor photorefractive quantum wells belong to materials with strong optical nonlinearity. One of the parameters that may affect the course of nonlinear phenomena in these materials is the electron and hole trapping coefficient. We present the results of a numerical analysis aimed to find out how electric field-dependent trapping coefficients affect the process of space-charge field formation in multiple quantum wells in the phenomenon of photorefractive twowave mixing.Photorefractive multiple quantum wells are characterized by high sensitivity and relatively short response time [1][2]. A characteristic feature of these materials is the occurrence of bipolar transport. This reduces the impact of diffusion on the phenomenon and necessitates the application of an external electric field. For GaAs/AlGaAs structures working in Franz-Keldysh geometry (electric field applied parallel to quantum wells), it is observed that electron mobility depends on field intensity. This phenomenon affects the course of two-wave mixing, causing the shift of a space-charge field relative to the interference pattern and enabling oneway exchange of energy between the waves [1][2][3].Another parameter that may have an impact on the course of nonlinear phenomena is the electron and hole trapping coefficient. The study [5] presents the influence of a strong electric field on the values of cross-sections for recombination to traps for bulk GaAs with EL2 defects. On the other hand, in studies of photorefractive two-wave mixing in GaAs/AlGaAs quantum wells the authors adopt a fixed value of these coefficients [1][2][3][4]. This approach is justified in the case of a small contrast of the interference pattern. Since experimental works often involve systems with deep modulation of light intensity, in which there are large local changes of electric field intensity, it is worth examining what the influence of the field dependence of carrier trapping coefficients is. In this work, we present numerical studies of the impact of this relation on the process of space-charge field formation under the stationary interference pattern.The photorefraction phenomenon in semi-insulating materials can be described with the band transport model PDDT (photogeneration -diffusion -drift -trapping) [2]. In descriptions of semiconductor structures the occurrence of one level of deep traps and one level of shallow dopants in the energy gap is usually assumed.Here we scrutinize the material in which shallow dopants are acceptors with concentration , whereas donors with concentration play the role of deep trapping levels. The relationship between the concentrations of donors and acceptors is described by the compensation coefficient . In addition, we assume the total ionization of shallow acceptors, i.e.. They do not take part in photorefractive transitions, but have an important impact on the initial concentration of ionized donors. Ionized donors with the concentration act as trap centers for electrons, while non-ionized donors with the concentration...

Abstract-Semi-insulating GaAs/AlGaAs multiple quantum wells are photorefractive materials with high sensitivity and short response time. Semi-insulation of these structures is commonly obtained by proton implantation. We present the measurements of photoconductivity in the samples with different proton doses. The results were compared to the theoretically predicted relationship between photoconductivity and the donor to acceptor concentration ratio. This allows to estimate the impact of proton dose on deep donor concentration.

Abstract-A method is proposed to determine mobility-lifetime products of photoexcited electrons and holes in semi-insulating GaAsAlGaAs quantum wells structures. The method is based on photoconductivity measurements and optical investigation of photorefractive material response in a wave-mixing setup using the running grating technique.