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Carbon-doped n-type nanocrystallineFeSi2/p-type Si heterojunctions were successfully prepared by pulsedlaser deposition. Their photodetection performances were evaluated using a 1.33µm laser at room temperature. Thebuilt-in potential of the heterojunctionsis approximately 0.92 eV. These heterojunctions exhibited a good rectifyingaction by more than two orders of magnitude at bias voltages of ±1 V. Thephotodetection was observed with a ratio of the current under illumination tothe dark current by more than one order of magnitude at - 1 V. The responsivityand quantum efficiency at - 1 V were estimated to be 23.3 mA/W and 2.2%,respectively. The estimated detectivity, which was higher than that of theheterojunctions comprised of undoped NC-FeSi2 films, was to beapproximately 1.0 × 1010 cm√Hz/W at - 1 V. This should be becausethe reduction of carrier density in NC-FeSi2 and the interfacestates by carbon doping.