Modified Poole–Frenkel mechanisms in Ge25BixSb15−xS60 thin films

The current–voltage (I–V) characteristics of amorphous Ge25BixSb15−xS60 (x=0, 5, 10 and 15) thin film samples sandwiched between metal electrodes have been investigated as a function of composition, deposition rate (0.61–2.65 nm s−1), film thickness (128.6–598.2 nm) and temperature (130–373 K). The current–voltage characteristics are ohmic in the lower field regime followed by non-ohmic behavior in the higher voltage regime, which has been satisfactorily explained by the modified Poole–Frenkel effect. The experimentally determined values of Poole–Frenkel factor (βPF) for different film composition, deposition rate and thicknesses are in good agreement with the theoretically calculated values. Fitting the room temperature data with Jonscher’s field-independent re-trapping model is an indication that a modified Poole–Frenkel process is operating. The Hall model can account for the low-temperature dielectric constant, and gives an indication of modified Poole–Frenkel emission.