A new family of photodetectors based on hydrogenated amorphous silicon (a-Si:H) and silicon carbide (a-SiC:H) is described. They are p-i-n photodiodes whose thin layers are grown by glow discharge on cheap substrates as glass or flexible materials. Modulating the absorption profile in the semiconductor and the thickness of the layers, it is possible to select, during the growing process, the wavelength range where the photodetector is more sensitive. A first generation prototype of photodetectors optimized for UV detection was tested at room temperature and with no external bias voltage, illuminating it with visible and vacuum-UV radiation. The results show that the measured quantum efficiency is above 15% in the 58.4 - 250 nm spectral range and about 300 times lower at longer wavelengths (0.05% at 700 nm). An improved second generation has been also tested in the same experimental conditions and the preliminary data exhibit a better noise level (less than 1 pA), a higher response stability and an enhanced efficiency. A linear dependence on the radiation intensity has been verified over three orders of magnitude at 400 nm. Noise figure evaluation and response times will be also presented.
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