Integrated all-silicon color filtering element with an enhanced wavelength tunability

A method for applying the wavelength-dependent response of silicon photodiodes for the integration of an electronically tunable optical filtering element with the photodetector in silicon is presented. Previous sensors suffered from a limited tunable spectral range. Here, the filter tunability is extended by enhancing the long-wavelength tunability using an extra implantation for realizing a higher doped buffer layer underneath a shallow junction to reduce the built-in depletion layer. Also, an independent electronically programmable short-wavelength cutoff is introduced. The latter is based on the control of the surface space-charge region. The flexibility obtained allows the electronic shaping of clearly distinguishable responses using a single photodiode.<>