Broad spectral response to photon energy unlimited by Schottky barrier from NiSi/Si junction

Recent advances in plasmonic absorption devices offer a novel approach for extending the range of silicon light detection. This is achieved by exploiting the Schottky interface energy barrier, which overcomes the limitation of the 1.12 eV photon energy conversion imposed by the silicon intrinsic bandgap. Internal photoemission has been widely accepted as the primary emission mechanism, which is mostly limited by the Schottky barrier height. However, we have discovered that carriers with energy lower than the Schottky barrier can generate electrical responses through the photothermal effect, breaking this restriction. In this study, we closely investigate two forms of photoresponses, namely photoelectric and photothermal, on a NiSi thin film Schottky photodetector, considering various factors such as temperature, applied bias, incident power, and wavelength regime. Without photothermal assistance, the device achieves a responsivity of 0.41 mA/W to a 1550 nm laser. Under bias-driven conditions, highly energized hot carriers generate a 2.18 mu A photoelectric response, while a 0.861 mu A photothermal response is simultaneously observed under 6 mW 1550 nm laser illumination. Through systematic investigation, we advance the mechanism of both responses by combining the hot carrier model and the Schottky barrier diagram. Finally, we experimentally obtain a 4.85 mu A sheer photothermal response to a 0.475 mW 4-mu m wavelength signal with 10.21 mA/W responsivity. It is expected that the device will also show responses to longer wavelengths.

Automated summary

Recent advances in plasmonic absorption devices have provided a new approach to extend the range of silicon light detection by exploiting the Schottky interface energy barrier. Internal photoemission is the primary emission mechanism, but we have discovered that carriers with energy lower than the Schottky barrier can generate electrical responses through the photothermal effect. We investigated photoelectric and photothermal responses on a NiSi thin film Schottky photodetector, considering factors such as temperature, applied bias, incident power, and wavelength regime.