Color filters integrated with the detector in silicon

The usual single-chip color imager consists of an alternating pattern of three types of color filters deposited on top of a regular array of photodetectors. The novel principle to be presented is comprised of a method for integrating the filtering element with the photodetector in silicon, which reveals an intrinsic color filtering capability based on the strong wavelength dependence of the absorption coefficient. The band-pass central wavelength of the optical filter is electronically tunable using the reverse voltage applied across the diode, so that only one diode is required for each color element.