Study of the mobility activation in ZnSe thin films deposited using inert gas condensation

ZnSe thin films were synthesized on glass substrates using the inert gas condensation technique at substrate temperature ranging from 25 °C to 100 °C. The hexagonal structure and average crystallite size (6.1-8.4 nm) were determined from X-ray diffraction data. The transient photoconductivity was investigated using white light of intensity 8450 lx to deduce the effective density of states (Neff in the order of 1.02 × 1010-13.90 × 1010 cm−3), the frequency factor (S in the range 2.5 × 105-24.6 × 105 s−1) and the trap depth (E ranging between 0.37-0.64 eV) of these films. The trap depth study revealed three different types of levels with quasi-continuous distribution below the conduction band. An increase in the photoconductivity was observed as a result of the formation of potential barriers (Vb) and of the increase of carrier mobility at the crystallite boundaries. The study of the dependence of various mobility activation parameters on the deposition temperature and the crystallite size has provided better understanding of the mobility activation mechanism.