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Proceedings Paper

Back-illuminated photodiodes for multislice CT: an estimation of temporal and spatial properties by carrier diffusion modeling
Author(s): Randy P. Luhta; Rod Mattson; Narayan Taneja; Peter Bui
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Paper Abstract

A back illuminated photodiode (BIP) has been developed for multislice CT which enables a CT scanner to be made with a large number of slices. Light absorbed on one surface of the photodiode generates charge carriers which diffuse through the silicon bulk to charge collection anodes on the opposite side. It is this minority carrier diffusion through the bulk which governs the spatial and temporal properties of the photodiode. The diffusion of carriers in the silicon is described by a partial differential equation (PDE) which can be solved numerically for a given geometry. Modeling carrier diffusion allows one to determine the risetime and response profiles for a given photodiode design without the expense of fabricating an actual device. The PDE for carrier diffusion has been solved for different BIP geometries using the Matlab PDE toolbox. This software uses the finite element method in two dimensions. Risetime and response profiles have been simulated for the same geometries as BIP devices that have been fabricated. The simulation results are in good agreement with the measurements done on actual devices. New geometries are also simulated to show how the BIP can be optimized.

Paper Details

Date Published: 6 May 2004
PDF: 12 pages
Proc. SPIE 5368, Medical Imaging 2004: Physics of Medical Imaging, (6 May 2004); doi: 10.1117/12.534626
Show Author Affiliations
Randy P. Luhta, Philips Medical Systems (United States)
Rod Mattson, Philips Medical Systems (United States)
Narayan Taneja, UDT Sensors, Inc. (United States)
Peter Bui, UDT Sensors, Inc. (United States)


Published in SPIE Proceedings Vol. 5368:
Medical Imaging 2004: Physics of Medical Imaging
Martin J. Yaffe; Michael J. Flynn, Editor(s)

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