Photocarrier dynamics in Cd0.96Zn0.04Te measured byoptical-pump terahertz-probe spectroscopy br

Photogenerated carrier relaxation process and terahertz conductivity of Cd0.96Zn0.04Te are investigated byoptical pump-terahertz probe spectroscopy at room temperature. With photoexcitation at 800 nm, thephotogenerated carrier recovery process can be fitted with a single exponential curve, and its recovery time lastsseveral nanoseconds, which decreases with the increase of photogenerated carrier densities in a certain range ofphotogenerated carrier densities, relating to the radiative recombination of electron-hole pairs. The transienttransmittance change of terahertz pulse remains the same with the photogenerated carrier densities increasingfrom 4.51x1016 cm-3 to 1.81x1017 cm-3, which is because the number of loss carriers by defect trapping isapproximate to the augment of carriers by photoexcitation. As the photogenerated carrier density increasesfrom 1.81x1017 cm-3 to 1.44x1018 cm-3, the magnitude of photoinduced absorption increases linearly with theincrease of photogenerated carrier density due to the fact that most of the defects are occupied. When thephotogenerated carrier densities are higher than 1.44x1018 cm-3, the magnitude of photoinduced absorptionremains almost the same, because the absorption of 800 nm pump pulse reaches a saturation level. Theevolution of complex conductivity with photogenerated carrier density in a delay time of about 50 ps can bewell fitted with Drude-Smith model. Our analysis provides an important data support and theoretical basis fordesigning and fabricating of Cd1-xZnxTe detection