Effect of deep traps on photo-generated carrier dynamics in high-resistivity CdTe

The effect of intragap trapping levels on transport dynamics of photo-generated charge carriers in semi-insulating CdTe:In bulk crystals is investigated, by means of nanosecond time-resolved photocurrent and electro-optic measurements. By using below-bandgap photon energies, electrons and holes dynamics have been independently studied. Hole current contribution dominates at lower photon energies, leading to faster recovery times, while the electronic component dominates transport on a 100 ns time scale. The evolution of local electric field on a ms time scale is due to charge trapping into deep states. By comparing experimental results with an ad hoc developed drift-diffusion model, intragap energy levels and trapping parameters are obtained.