A Self-Powered Heterojunction Photodetector Based on a PbS Nanostructure Grown on Porous Silicon Substrate

A photosensor was fabricated based on a lead sulfide (PbS)/porous silicon (Ps) heterojunction. An n-type Si(100) single crystal wafer was used to prepare the Ps using a photo-electrochemical etching method. A PbS nanocrystalline thin film was deposited onto the Ps substrate using a microwave-assisted chemical bath deposition (MA-CBD) technique. The current-voltage (I-V) characteristics of the fabricated PbS/Ps photosensor were studied under dark, 10 mW/cm(2), 20 mW/cm(2), and 40 mW/cm(2) illumination by light. The device shows good response to light even without a bias voltage and the sensitivity when the applied voltage is 0 V decreased from 5.66 x 10(4) % under 10 mW/cm(2) to 1.8 x 10(3) % when the device is illuminated by 40 mW/cm(2) intensity light. The fabricated PbS/Ps photdetector shows a faster response to light of 0.43 sec when the applied voltage and intensity of light were 1.0 V and 40 mW/cm(2), respectively. Moreover, the fastest fall time was 0.4 sec obtained for the device that was exposed to 40 mW/cm(2) light and biased by 0.75 V.