Abstract
Broadband photosensors have been widely studied in various kinds of materials. Experimental results have revealed strong wavelength-dependent photoresponses in all previous reports. This limits the potential application of broadband photosensors. Therefore, finding a wavelength-insensitive photosensor is imperative in this application. Photocurrent measurements were performed in Sb2Te3 flakes at various wavelengths ranging from visible to near IR light. The measured photocurrent change was insensitive to wavelengths from 300 to 1000 nm. The observed wavelength response deviation was lower than that in all previous reports. Our results show that the corresponding energies of these photocurrent peaks are consistent with the energy difference of the density of state peaks between conduction and valence bands. This suggests that the observed photocurrent originates from these band structure peak transitions under light illumination. Contrary to the most common explanation that observed broadband photocurrent carrier is mainly from the surface state in low-dimensional materials, our experimental result suggests that bulk state band structure is the main source of the observed photocurrent and dominates the broadband photocurrent.
Highlights
The interaction of light with matter has been a widely used technique for light sensors and is widely used in our daily life and scientific research
We study the photoresponse of Sb2 Te3 flakes
Our analysis shows that the corresponding energies of these measured photoresponsivity peaks and dips at different light wavelengths are consistent with the energy difference of Density of states (DOS) peaks between conduction and valence bands
Summary
The interaction of light with matter has been a widely used technique for light sensors and is widely used in our daily life and scientific research. In addition to the higher surface ratio, earlier studies have demonstrated that carrier mobility is one of the most critical factors for determining the light responsivity [7,8] With these considerations in mind, nanostructures and low-dimensional systems with high mobility have been widely investigated [9–16]. Previous reports have revealed that the photoresponses show a strong wavelength-dependent deviation in these systems [10,15,19–49] This inhomogeneous response would limit the potential applications of these materials as broadband photosensors. The light penetration into the material and carriers from the bulk state of the topological material might contribute to the measured photocurrent This might be one of the reasons behind the observed strong wavelength dependence in the previous reports [50]. The low-deviated band structure of bulk state leads to the behavior of the observed uniform broadband light responsivity
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