The energy distribution of localized states in amorphous arsenic triselenide from transient photoconductivity measurements

DC conductivity, time of flight (TOF) and transient photoconductivity (TP) measurements were performed in order to characterize samples of amorphous arsenic triselenide prepared by thermal evaporation. Analysis of the hole carrier drift mobility data provides strong evidence for carrier interaction with a structured distribution of defect centres rather than the broad featureless distribution that has in the past been proposed for arsenic triselenide. Deviations from power law behaviour in the TP data also provide evidence for the existence of structure. We applied the 'intuitive' thermalization spectroscopic technique to the data and discovered defect centres situated at an energy position E 2 approximately 0.42 eV within the mobility gap. At high temperature the thermalization depth of holes is limited by a set of recombination centres situated at E 1 approximately 0.65 eV above the valence band edge.