UV photo-responsivity of a large-area MWCNT-Si photodetector operated at cryogenic temperature

In the last decades much effort has been addressed to realize novel solid state photo-detectors with a high quantum efficiency in the UV wavelength region to be used in experiments detecting Cherenkov or fluorescence radiation even at cryogenic temperatures. Among the possible devices with these characteristics, the large-area solid detectors made of n-doped silicon substrate coated with Multi-Walled Carbon Nanotubes (MWCNTs) appear to be particularly promising since they combine the great UV radiation absorbance of MWCNTs (at about 200 nm) with their unique characteristics for electrical conductivity and mechanical resistance at low temperatures. In this work we present the cryogenic characteristics of a MWCNT-Si large-area (1 cm2) photo-detector, in which a UV photo-sensitive heterojunction is obtained growing, by Chemical Vapour Deposition (CVD), multi-walled carbon nanotubes on an n-type silicon substrate. Measurements have been made at various temperatures in the range from 5K to 300K by illuminating the photo-detector with a 378 nm UV continuous laser light source. Results demonstrate the capability of such device to be successfully employed in cryogenic experiments as well at room temperature with high stability and high photon detection efficiency in the UV region.