Comparative Characterization of PbS Macro- And Nano-Crystalline Photoresistive Detectors

A comparative study of photodetector performance for nano- and micro-crystalline PbS thin layers is presented. Both types of PbS films were obtained using the Chemical Bath Deposition method. To prepare nano-crystalline thin films we used a short reaction time with no doping Bi added. At low levels of irradiance (0.1 m W/cm²) and room temperature (RT), the macro-crystalline PbS outperforms its nano- crystalline counterpart, by a factor of 6 for the value of DeltaR/R_dark However the nano-crystalline photodetectors show significantly lower optical quenching for large values of irradiance (ap 500 mW/cm²) at RT and better DeltaR/R_dark performance at lower temperature, with an optimum temperature of 150 K. The low frequency noise behavior is a superposition of 1/f flicker noise at low frequency and generation-recombination and thermal noise at higher frequency. The proportionality factor between the 1/f noise and the DC dark current for the series resistor is 1.5 times larger for the nano-crystalline photodetector at room temperature.