We report on lateral pin germanium photodetectors selectively grown at the end of silicon waveguides. A very high optical bandwidth, estimated up to 120GHz, was evidenced in 10 µm long Ge photodetectors using three kinds of experimental set-ups. In addition, a responsivity of 0.8 A/W at 1550 nm was measured. An open eye diagrams at 40Gb/s were demonstrated under zero-bias at a wavelength of 1.55 µm.
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.
The transient photocurrent response of a vertically stacked triple pn junction structure, which can detect three different colours simultaneously, is investigated. The triple pn junction structure is designed based on the effect that the penetration depth in silicon depends on light wavelength. To increase the bandwidth of optical sensor systems the transient photocurrent response is a critical parameter. The transient response is measured by applying three different light wavelengths to this triple junction structure. This triple pn junction structure is fabricated in a 0.6 µm BiCMOS technology using a p−p+ epitaxial wafer without any process modification. Based on the measurement results, it can be concluded that this triple pn junction structure can be applied to optical sensors without optical filters and the total data rate of this structure can reach up to 100 Mbit/s.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.