Persistent photoconductivity inZn0.04Cd0.96Te semiconductor thin films

Persistent photoconductivity (PPC) has been observed up to room temperature in ${\mathrm{Zn}}_{0.04}$ ${\mathrm{Cd}}_{0.96}$Te 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.