CdS based novel photo-impedance light sensor

A novel photo-impedance (hybrid photocapacitive-photoresistive) sensor for visible light employs gated cadmium sulfide photoresistance connecting two fixed capacitances. The changes of the photoresistance and of the metal–insulator (dielectric)-semiconductor (MIS) under illumination affect the overall device capacitance. The MIS and photoresistor frequency dispersion allows for increasing the dynamic range by measuring the capacitance response at lower frequencies. By making this device a part of the tank circuit of a radio frequency oscillator, the information on illumination intensity can be relayed as the signal frequency and detected remotely. (paper)