Cross-talk reduction and efficiency of integrated photodiodes shown by an integrated edge detector

authored by: Ingo Martiny, Ruediger Leuner, Bernhard Wicht
Abstract: This paper describe the limits for the efficiency of integrated photodiode arrays in a standard CMOS-process. It shows that an efficiency of more than 60% is not possible for wideband incident light. The efficiency depends on the area of the diodes, the distance between the diodes and the depth of the diode junction. The resulting efficiency of integrated photodiodes in a 0.8 μm-CMOS-process is shown. For these photodiodes two ways of crosstalk reduction between photodiodes arranged in a line or a 2-D array are introduced. Injecting a substrate current between the diodes, the cross-talk can be reduced in a controlled way by the magnitude of the current. Another possibility is to embed every diode in a separate well. The advantages and disadvantages of both systems are discussed. Finally, an application of integrated photodiodes in an edge detector IC is presented. This 6 mm² circuit has been manufactured in a 0.8 μm process using embedded photodiodes for crosstalk reduction. The circuit performs a position measurement of a shade edge or contrast edge imaged onto its photodiode array. With its all-analog signal processing, even semitransparent media can be detected without precision tradeoffs.
Organisation(s): Mixed-Signal Circuits Section
External Organisation(s): MAZ Germany GmbH
Type: Conference article
Journal: Proceedings of SPIE - The International Society for Optical Engineering
Volume: 3950
Pages: 39-48
No. of pages: 10
ISSN: 0277-786X
Publication date: 2000
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Computer Science Applications, Applied Mathematics, Electrical and Electronic Engineering