Noise in PbS IR photoresistors

Abstract

PbS photoconductors have been fabricated by the chemical deposition method onto glass substrates. The investigated samples prepared from layers deposited 20 years ago. The photoconductivity of free and encapsulated detectors was investigated at room temperature. The performance of PbS detectors was practically not changed after long time storage at laboratory conditions, or easily recovered after vacuum treatment at 75 o C. The low-frequency (10Hz…20 kHz) noise spectra were measured in dark and during infrared exposure. The carrier lifetime was determined by measuring the frequency response of the device. The changes of the resistance during infrared and ultraviolet exposure were measured too. After the UV illumination the magnitude of the noise levels did not changed too much, however the character of the spectra has definitely changed. The spectra became similar to 1/f indicating that the dominance of generationrecombination noise is less pronounced. The persistent conductivity increase, which occurred by the ultraviolet light is interpreted as the hydration of the oxidized surface.