APPLICATION OF THE INTERRUPTED FIELD TIME-OF-FLIGHT TRANSIENT PHOTOCONDUCTIVITY TECHNIQUE TO INVESTIGATING SAMPLE INHOMOGENEITIES - CL-DOPED AMORPHOUS SE-TE AND SE-AS FILMS

The interrupted field time-of-flight (IFTOF) technique was applied to Cl-doped amorphous Se:Te and Se:As photoreceptor-type films to investigate the variation of the hole lifetime across the firm due to sample inhomogeneities. By interrupting the hole photocurrent at different positions across the film, it was possible to obtain the variation of the hole lifetime, tau, across a photoreceptor film up to about two-thirds of the film thickness. For Cl-doped Se0.953Te0.047 films (46 at. ppm Cl), the Te content was uniform in the bulk, which resulted in the hole lifetime also being uniform. An important inference was that the Cl-content profile must therefore also be uniform. In the case of Cl-doped a-Se:0.2%As films (10 at. ppm Cl), the As concentration across the film was not uniform because of fractionation effects during vacuum deposition. The variation of the hole lifetime across the a-Se:As film correlated well with the As-concentration profile obtained from electron probe X-ray microanalysis. The present paper demonstrates the usefulness of the IFTOF technique for studying such inhomogeneities.