A Schottky infrared photodetector with dual mechanisms, where both photoelectric and photothermal current generation mechanisms coexist is presented. The dominant role of these mechanisms changes with surface passivation process. In the device without passivation process, the device exhibits high responsivity due to the presence of the photothermal effect but has slow rise and recovery times. However, after surface passivation treatment, the device characteristics are dominated by the photoelectric effect, showing a significantly faster response time, capable of detecting signal level changes within less than 80 ms, with a constant current difference between on and off states. This unique multifunctionality promotes the development of Schottky device capable of achieving multiple optical detection purposes
The metal-semiconductor interface structure, which can convert photon energy into electrons by internal photon-emission effect, is utilized as one kind of photodetectors. In the Schottky device, the barrier limits the detectable wavelength and the detection response, so how to amplify the detection signal is an important issue. Here, we first quantify the effect of applied bias on the energy barrier reduction mechanism from a mathematical equation. Furthermore, we fabricate metal/semiconductor Schottky devices and experimentally demonstrate the optimization of optical response by image-force lowering effect. As a result, experiment showed a 21 times enhancement in responsivity after an image-force lowering effect was induced.
Current mid-infrared detection technologies dominating the market are mainly based on group III-V semiconductors. These devices have detection range depending upon the materials and also drawbacks like complex and expensive fabrication process, and incompatibility with CMOS processes. To overcome these complexities, silicon-based photodetectors using low cost approaches offer the excellent alternative. The current commercialized silicon-based detector technologies exhibit detection capabilities up to 1100 nm. Here, we have presented a metal–semiconductor silicon-based detectors showing a wider detection range extending from visible light to mid-infrared region. In this work, we investigate a silicon based Schottky diode photodetectors with a thin Ag film of thickness 10 nm over a silicon substrate for detecting radiation emitted from mid-infrared light source. Using lock-in amplifier for further measurement, not only the quality of signal was increased, the detection range of the device is enhanced up-to 5300 nm, which is far beyond the current limit of silicon-based detectors. Hence, the Schottky device used in this study has the potential to detect radiation up to mid-infrared wavelengths. On the other hand, the relative level of noise generated also increases with wavelength, so the detection signal gets buried. These signals have been successfully extracted and analyzed using the technology of Lock-in Amplifier.
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