Electrical transport properties of sensitized PbSe thin films for IR imaging sensors

Abstract

Electrical transport properties of sensitized PbSe thin films for IR imaging applications were investigated. PbSe thin films were deposited by Chemical Bath Deposition (CBD) method. To sensitize the film, oxidation at 460 °C and iodization at 350 °C were performed successively. As-grown PbSe thin films showed p-type conduction due to Se-rich condition with carrier concentrations, mobility of and electrical resistivity of PbSe thin film after oxidation, the carrier density, mobility and resistivity values were and However, the carrier type was still p-type after oxidation. After sensitization (oxidation and iodization), PbSe thin film showed p-type behavior with carrier concentration of mobility of and resistivity of Iodine-rich PbI2 phase is formed on the top part of the film after iodization. Therefore, this I-rich PbI2 phase still generates p-type conduction without any carrier inversion. A PbI2/PbSe thin film structure showed pp isotype heterojunction characteristics after sensitization. No photoluminescence (PL) signal was observed from as grown thin films and oxidized PbSe thin film showed a peak at 285 meV. After sensitization, a significantly intense IR fluorescence peak from the band gap at 291 meV was observed. The peak height from sensitized PbSe thin film is 12 times higher than that of oxidized PbSe possibly the recombination of photo-generated electron-hole pairs was effectively suppressed. In addition, dark current as a function of temperature in as-grown, oxidized and sensitized PbSe was investigated and results showed the grain boundary activation energy values of 31 meV, 57 meV and 96 meV respectively, which may act as a sensitizing center for electron trapping. In summary, electrical properties data for as grown, oxidized and sensitized PbSe thin films are presented and temperature dependence studies indicates electron trapping mechanism for photoconductivity.