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Proceedings Paper

A low-noise 15-µm pixel-pitch 640x512 hybrid InGaAs image sensor for night vision
Author(s): Fabrice Guellec; Sébastien Dubois; Eric de Borniol; Pierre Castelein; Sébastien Martin; Romain Guiguet; Michaël Tchagaspanian; Anne Rouvié; Philippe Bois
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Paper Abstract

Hybrid InGaAs focal plane arrays are very interesting for night vision because they can benefit from the nightglow emission in the Short Wave Infrared band. Through a collaboration between III-V Lab and CEA-Léti, a 640x512 InGaAs image sensor with 15μm pixel pitch has been developed. The good crystalline quality of the InGaAs detectors opens the door to low dark current (around 20nA/cm2 at room temperature and -0.1V bias) as required for low light level imaging. In addition, the InP substrate can be removed to extend the detection range towards the visible spectrum. A custom readout IC (ROIC) has been designed in a standard CMOS 0.18μm technology. The pixel circuit is based on a capacitive transimpedance amplifier (CTIA) with two selectable charge-to-voltage conversion gains. Relying on a thorough noise analysis, this input stage has been optimized to deliver low-noise performance in high-gain mode with a reasonable concession on dynamic range. The exposure time can be maximized up to the frame period thanks to a rolling shutter approach. The frame rate can be up to 120fps or 60fps if the Correlated Double Sampling (CDS) capability of the circuit is enabled. The first results show that the CDS is effective at removing the very low frequency noise present on the reference voltage in our test setup. In this way, the measured total dark noise is around 90 electrons in high-gain mode for 8.3ms exposure time. It is mainly dominated by the dark shot noise for a detector temperature settling around 30°C when not cooled. The readout noise measured with shorter exposure time is around 30 electrons for a dynamic range of 71dB in high-gain mode and 108 electrons for 79dB in low-gain mode.

Paper Details

Date Published: 15 February 2012
PDF: 8 pages
Proc. SPIE 8298, Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII, 82980C (15 February 2012); doi: 10.1117/12.912105
Show Author Affiliations
Fabrice Guellec, CEA-LETI Minatec (France)
Sébastien Dubois, CEA-LETI Minatec (France)
Eric de Borniol, CEA-LETI Minatec (France)
Pierre Castelein, CEA-LETI Minatec (France)
Sébastien Martin, CEA-LETI Minatec (France)
Romain Guiguet, CEA-LETI Minatec (France)
Michaël Tchagaspanian, CEA-LETI Minatec (France)
Anne Rouvié, III-V Lab. (France)
Philippe Bois, III-V Lab. (France)

Published in SPIE Proceedings Vol. 8298:
Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII
Ralf Widenhorn; Valérie Nguyen; Antoine Dupret, Editor(s)

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