Persistent photoconductivity in Zn0.04Cd0.96Te semiconductor thin films

Persistent photoconductivity (PPC) has been observed up to room temperature in Zn0.04Cd0.96Te semiconductor thin films which were prepared by the laser ablation method. The decay of PPC in these materials follows a stretched-exponential function with very long lifetimes. A comparison of experimental results of PPC has also been obtained for the original bulk samples. Our results indicate that deep centers are responsible for the PPC observed in thin-film samples. A peculiar overshoot behavior in the PPC buildup transient has been observed at higher temperatures, which suggests that the deep center, when filled with an electron, has two possible states, a stable state and a metastable state. The decay-time constant τ and exponent β as functions of temperature have been measured in the thermally activated temperature region, from which the electron capture barrier has been determined. The PPC decay-time constants at different excitation photon dose levels have been measured.