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Proceedings Paper

Correlating buried-finger photodetector for time-of-flight applications
Author(s): G. Zach; A. Nemecek; K. Oberhauser; H. Zimmermann
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Paper Abstract

A double-cathode photodetector (DCP) featuring a buried-finger structure to achieve improved separation efficiency is presented. The interleaving comb-shaped cathodes are realized with n-buried implants and they are located in the p-epitaxial layer roughly 1μm below the surface. Based on MEDICI device simulations several layout variations have been realized in a slightly modified BiCMOS process. Best results are achieved with a finger distance of 12μm and a finger width of 1μm: separation efficiencies of 50, 67, and 54% and responsivities of 0.23, 0.47, and 0.38A/W were measured for the optical wavelengths 410nm, 660nm, and 850nm, respectively. All test structures occupy optical active areas of around 100×100μm2. A maximum 3dB-modulation bandwidth of almost 300MHz was measured, while dark currents in the picoampere range are typical for these detectors up to a bias voltage of 5V at room temperature. In the application of a time-of-flight (TOF) distance measurement sensor, the DCP serves as optical detector and correlating device at the same time. Distance measurements up to 6.2m were performed with a 650nm laser source that emitted an average optical power of 1mW using rectangular modulation signals at 10MHz. The standard deviation is better than 1cm up to 3.4m for a total measurement time of 20ms per acquired distance point.

Paper Details

Date Published: 17 June 2009
PDF: 9 pages
Proc. SPIE 7389, Optical Measurement Systems for Industrial Inspection VI, 738936 (17 June 2009); doi: 10.1117/12.827817
Show Author Affiliations
G. Zach, Vienna Univ. of Technology (Austria)
A. Nemecek, Vienna Univ. of Technology (Austria)
K. Oberhauser, Vienna Univ. of Technology (Austria)
H. Zimmermann, Vienna Univ. of Technology (Austria)

Published in SPIE Proceedings Vol. 7389:
Optical Measurement Systems for Industrial Inspection VI
Peter H. Lehmann, Editor(s)

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