Thin-film photodetectors for the UV and vacuum UV spectral range

We present the first semiconductor p-i-n photodiode with excellent sensitivity in the VUV range and high rejection of visible radiation. The device is based on the thin-film technology of amorphous silicon and silicon carbide and can be integrated in large area arrays on glass or flexible substrate. Its internal quantum efficiency is over 50% in the VUV (at 58 nm) and decreases with wavelength. In the visible range the sensitivity can be tuned by variations to the technology parameters. Solar blind photodiodes have been fabricated, with 1% quantum efficiency at 400 nm and 0.1 at 650 nm Working bias voltage is very low since its best sensitivity is achieved when reversly biased with 0.3V. Linearity of the photocurrent was verified with incident UV light in the range 5nW to 4mW. Rensponse times under UV illumination was tested with a N-2 laser: 500 ns rise time and 6 mu s FWHM were measured. The excellent behaviour of the photodetector in the UV range was explained within the hypothesys that generation of hot carriers in the p-doped layer occurs and that a pure diffusion mechanism rules transport, beingf the thickness of the p-doped layer comparable with the effective diffusion length of electrons.