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Recent progress in plasmonic absorption devices provides a new way of photon-electron conversion through hot carrier emission if a carrier possesses sufficient energy to overcome the Schottky barrier. However, the behavior of carriers with energy lower than that of the barrier has rarely been discussed, while it could be very useful if the energy is converted efficiently. Very recently, the photothermal effect, which used to be treated as an energy loss, is used to detect low energy photons. Here, we systematically and quantitatively analyzed the mechanism of this effect, which, to the best of our knowledge, has not yet been determined stringently. A very thin layer of Ni is deposited on n-type Si (n-Si) with an electron-beam evaporator, and annealed by rapid thermal processer to form a NiSi/n-Si Schottky junction. The device was measured under intermittent light illumination with several incident power and bias. Under 0.05 V forward bias, the device generates a photothermal assisted response, which is boosted by 23% of the traditional photoelectric response at 1550 nm in 5 s. The response in different incident wavelengths is also presented in this work. The photothermal response is caused by low energy carriers, which dissipates thermally and heats the interface locally, causing the change of the electrical characteristics of the device. This effect could be used to detect signals regardless of wavelength and has a potential in future low energy photon conversion technology.
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