Spectrum Selectivity and Responsivity of ZnO Nanoparticles Coated Ag/ZnO QDs/Ag UV Photodetectors

Photoresponsivity and spectrum selectivity of ZnO nanoparticles (NPs)-coated colloidal quantum dots (CQDs)-based Ag/ZnO QDs/Ag interdigitated metal-semiconductor-metal (MSM) photodetectors under front and back illuminations have been investigated in this letter. It is shown that the ZnO NPs film coated over the interdigitated MSM photodetector acts as a filter layer to enhance the spectrum selectivity at the cost of reduced responsivity of the detector under front illumination. Whereas, the same NPs layer acts as a scattering medium to enhance the responsivity at the cost of reduced selectivity of the detector under back illumination condition. The measured responsivity under front illumination is 6 A/W with a full width at half maxima (FWHM) of ~25 nm, whereas it is increased to 20 A/W with an FWHM of ~49 nm under back illumination at an applied bias of 2 V. Thus, the ZnO NPs layer can be used to optimize the photoresponse characteristics of the ZnO CQDs-based MSM photodetector by changing the direction of illumination on the device.