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See detailIntegrated photometer with porous silicon interference filters
Hunkel, D.; Marso, Michel UL; Butz, R. et al

in Materials Science & Engineering : A (2000), B69-70((2000)), 100-103

Porous silicon transmission interference filters with laterally varying transmission wavelengths are used to manufacture a photometer. Because of the linear varying transmission characteristic of the ... [more ▼]

Porous silicon transmission interference filters with laterally varying transmission wavelengths are used to manufacture a photometer. Because of the linear varying transmission characteristic of the filter it is possible to measure, beyond small regions of the porous layer, the correlated spectral photo current. It is therefore necessary to bring up a series of ohmic metal contacts along the porous filter. Between two neighbouring contacts one can measure the spectral photo current of the transmission wavelength at this specific point of the surface. By measuring multiple pairs of contacts, the whole spectrum between 400 and 1100 nm wavelength can be recorded. First results of the resolution capability and sensitivity are demonstrated. [less ▲]

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See detailInterference filters from porous silicon with laterally varying wavelength of reflection
Hunkel, D.; Butz, R.; Arens-Fischer, R. et al

in Journal of Luminescence (1999), 80(1999), 133-136

Porous silicon reflection interference filters of Bragg type consists of up to 40 quarter wave layers with alternating high- and low-refraction index. The refraction index depends on the porosity of the ... [more ▼]

Porous silicon reflection interference filters of Bragg type consists of up to 40 quarter wave layers with alternating high- and low-refraction index. The refraction index depends on the porosity of the silicon. The reflection wavelength can vary over a wide range and depends on the thickness and refraction index of the porous layers. A laterally continuously varying wavelength with linear profile of the filter can be achieved by manipulating the porosity and thickness of the silicon in the lateral direction. Our approach is to vary the Fermi level laterally by applying a potential parallel to the surface of the wafer. The slope of the Fermi level is easily controlled by the magnitude of the potential. The lateral current density and thus the porosity and thickness is related to the potential difference between the laterally varying Fermi level and the potential induced by the counter electrode. This relation is the well-known current-voltage characteristic of a Silicon hydrofluoric acid contact. The linearity of the etch profile across the wafer is demonstrated and the properties of preliminary reflection filters are shown. [less ▲]

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