No abstract

No abstract

A filter-less BiCMOS RGB colour sensor for wavelength detection in the wavelength range from 400 to 900 nm is presented. The sensor is based on the effect that light with longer wavelength penetrates silicon deeper than light with shorter wavelength. The detector is formed by three vertically stacked photodiodes: a deep diode used as the sensing element for red light, a middle diode to detect green light and a shallow diode as the blue light detector. The resulting RGB output is used to accurately determine the wavelength of the incident light. The sensor is fabricated in standard 0.6 mm BiCMOS technology without any process modifications.Introduction: Most conventional CMOS colour sensors are based on at least three photodetectors covered with RGB printed Bayer filters or interference filters. The three detectors themselves are inherently intensity detectors but have no colour selectivity. To add colour selectivity each detector is covered with a certain colour filter and records one distinct colour. The wavelength of the incident light is identified by combining the output signals of the three neighbouring detectors [1]. A major drawback of such tristimulus colour sensors is the need for additional filters and the increase of silicon area which adds to production costs.Filter-less RGB colour sensors with vertically arranged pn junctions (e.g. as described in [2,3]) eliminate these disadvantages. To our knowledge, however, such detectors have not yet been used for wavelength detection. In this Letter, we describe the accurate wavelength determination with three vertically-stacked photodiodes (two of them using the n+ buried layer) in a standard BiCMOS technology without any additional production steps.

No abstract

No abstract