Product of mobility and lifetime of charge carriers in CdTe determined from low-frequency current fluctuations

The model, which clarifies the low-frequency fluctuations of the current flowing in CdTe sample, makes it possible to determine the product of the mobility and lifetime of the charges in mentioned semiconductor. This model, with general validity for semiconductors, is based on the interaction of shallow traps with the valence or conduction band. As a result of the action of these centers, current fluctuations appear, the mean amplitude of which increases linearly with the inverse value of the frequency. It was found that the slope of this dependence is proportional to the product of mobility µ and a constant which is common to all shallow traps and which is denoted by the symbol a. The lifetime of charges located on shallow traps varies according to the relationship τ = a/f and for f_min it acquires a maximum value of τ_max, which agrees with the stationary lifetime. For the p-CdTe crystalline semiconductor the mobility-lifetime product µ_pτ_p = (6.6 ± 0.3) × 10^-7 cm²V^-1was obtained. Similar study of n-type CdTe showed µ_nτ_n = (7.5 ± 0.3) × 10^-8 cm²V^-1.