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Proceedings Paper

A novel JFET readout structure applicable for pinned and lateral drift-field photodiodes
Author(s): Andreas Süss; Bedrich J. Hosticka
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Paper Abstract

Enhancement of the dynamic range of photodetectors used in advanced image sensors such as time-of-flight sensors or image sensors for automotive applications is a major research topic. In this paper an improved unipolar readout structure is presented, that is superior to the widely employed source follower readout implemented by enhancement MOSFETs. It yields a high output voltage swing and low noise, while requiring no additional processing steps. The readout structure is consisting of a low-noise JFET whose gates are formed by a floating diffusion, thus preserving in-pixel accumulation capability - which additionally improves noise performance. This structure outperforms a simple in-pixel implementation of a JFET and a photodetector in terms of the necessary area consumption, thus improving fill factor. For pixels with a pitch of several microns this readout structure is a good trade-off between area, output voltage swing and, most important, noise performance. Furthermore, since only a ground connection is needed for application, fill-factor and power-grid disturbances like DC-voltage drop can be additionally improved.

Paper Details

Date Published: 9 May 2012
PDF: 8 pages
Proc. SPIE 8439, Optical Sensing and Detection II, 84391D (9 May 2012); doi: 10.1117/12.922431
Show Author Affiliations
Andreas Süss, Fraunhofer Institute for Microelectronic Circuits and Systems. (Germany)
Bedrich J. Hosticka, Fraunhofer Institute for Microelectronic Circuits and Systems. (Germany)

Published in SPIE Proceedings Vol. 8439:
Optical Sensing and Detection II
Francis Berghmans; Anna Grazia Mignani; Piet De Moor, Editor(s)

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