Charge transport in photosensitive nanocrystalline PbTe(In) films in an alternating electric field

Abstract Frequency and temperature dependences of the impedance components have been investigated in darkness and under illumination for PbTe(In) nanocrystalline films. Synthesis of the films was performed using evaporation of a target source to a cooled glass substrate. The films have a column-like structure with a mean grain size varying from about 60 nm to 170 nm depending on the deposition temperature. Analysis of the data obtained revealed that the conductivity of the films is determined by two mechanisms: charge transport along the inversion channels at the grain surface and activation through barriers at the grain boundary. Persistent photoconductivity appears in the films below T = 150 K. The frequency dependence of the relative photoresponse has a pronounced maximum. The photoresponse in the ac mode may be higher by two orders of magnitude than in the dc measurements.