Lead Selenide Thin Films Designed for Laser Sensing and Visible Light Communications

Abstract

Herein thin films of PbSe are coated onto amorphous glass, amorphous silicon (a−Si) and crystalline n−type Si (n−Si) wafers by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. The films are structurally, morphologically, compositionally, optically and electrically characterized. Strong effect of the nature (amorphous or crystalline) and type (Si or glass) of the substrate on the physical properties of lead selenide films is detected. Of these properties the crystallite sizes decreased and the microstrain, the stacking faults and defect density increased and the energy band gap is blue shifted when (a, n)-Si substrates replaces glass. In addition, the use of crystalline n−Si substrates instead of a−Si removed the free carrier absorption from a−Si/ p−PbSe improving the quantum efficiency of the devices. Opto-electronically, n−Si/p−PbSe films showed photosensor characteristics that suit both visible light and infrared technology applications. The photosensors displayed high current responsivity, external quantum efficiency percentages and response times reaching respective values of 1.4 A/W, 172% and 60 μs. In addition, the n−Si/p−PbSe photosensors which were used as detectors to receive wireless light signals generated from light pulses of 10 kHz frequencies showed smart features nominating them as promising devices for laser sensing and visible light communication technology.