Wavelength dependent photosensitivity modulation of Aluminium/Lead sulphide/Indium tin oxide back-to-back diode

The photosensitivity of aluminium (Al)/lead sulphide (PbS)/indium tin oxide (ITO) thin layered structure is investigated considering the photon wavelength dependent current-voltage and capacitance-voltage characteristics of the device. The current-voltage characteristics of the test structure are analyzed adopting the back-to-back Schottky barrier diode model. The diode possesses low dark current in contrast to the high value of photocurrents measured under different illumination wavelengths. The change in photocurrents with different illumination wavelengths clearly indicates the change in photo-sensitivity of the device. The capacitance-voltage characteristics of Al/PbS/ITO structure demonstrate a definite improvement of the device capacitance with the higher wavelength exposures. The matter is explained in terms of the additional capacitance owing to the excess carrier generation within the device under illumination. The photosensitivity modulation of the device can be exploited in photo-sensor or photo-detector applications in various electronic devices.