Abstract
Porous Si-SiO2 UV microcavities are used to modulate a broad responsivity photodetector (GVGR-T10GD) with a detection range from 300 to 510 nm. The UV microcavity filters modified the responsivity at short wavelengths, while in the visible range the filters only attenuated the responsivity. All microcavities had a localized mode close to 360 nm in the UV-A range, and this meant that porous Si-SiO2 filters cut off the photodetection range of the photodetector from 300 to 350 nm, where microcavities showed low transmission. In the short-wavelength range, the photons were absorbed and did not contribute to the photocurrent. Therefore, the density of recombination centers was very high, and the photodetector sensitivity with a filter was lower than the photodetector without a filter. The maximum transmission measured at the localized mode (between 356 and 364 nm) was dominant in the UV-A range and enabled the flow of high energy photons. Moreover, the filters favored light transmission with a wavelength from 390 nm to 510 nm, where photons contributed to the photocurrent. Our filters made the photodetector more selective inside the specific UV range of wavelengths. This was a novel result to the best of our knowledge.
Highlights
Porous silicon (PS) is a promising material for many different applications, such as solar cells, as anti-reflection coating [1], chemical sensing [2,3], biomedical applications [4], biosensing [5,6], as a photodetector [7], or light-emitting diode [8]
Luminescent silicon quantum dots embedded in free-standing PS and PS microcavity filter (MF) infiltered with CdSe/ZnS and AgInS2/ZnS quantum dots have been reported [21,22,23]
The authors mentioned that the localized mode of the MF modulated the photoluminescence of the quantum dots [22,23]; where electrical and thermal tuning of localized modes could be achieved by infiltrating liquid crystals in PS MFs [24]
Summary
Porous silicon (PS) is a promising material for many different applications, such as solar cells, as anti-reflection coating [1], chemical sensing [2,3], biomedical applications [4], biosensing [5,6], as a photodetector [7], or light-emitting diode [8]. ARCs are used to convert down the higher energy solar radiation into a wide range of light spectra, which is absorbed more efficiently into bulk Si [10]. In another interesting application, silver nanoparticles were infiltrated within a porous silicon photonic crystal to detect the trace of explosives (Rhodamine 6G dye and Picric acid explosives) using surface-enhanced Raman scattering [13]. This effect occurs because PS has less absorption at long wavelengths [16,17] This kind of filter can be lifted off from the Si substrate creating a free-standing PS MF. The first memristor showed properties of plasticity and short/long term memory, whereas the second exhibited strong filamentary-type resistance switching; and they have been used as two terminal resistive memory cells [27]
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