30 September 2009 Temperature-insensitive silicon photoconductor
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A temperature insensitive silicon photoconductor has been designed and produced, which significantly improves the detector performance over a wide operational temperature range. The detector Responsivity in conventional silicon photodetectors is a function of temperature. The Responsivity and the associated detector sensitivity can vary by as much as 600% over the normal operating temperature ranges of many commercial and military products. The temperature controlled photoconductor described in this paper incorporates a sheet resistance heater that is integrated into the silicon wafer structure. A closed loop control circuit operates the detector at an optimized temperature. This is done in a way so as to maximize the system signal-to-noise ratio, regardless of the temperature and background illumination level of the environment. The measured detector sensitivity improvement is approximately 6 times higher at the low end of the operational temperature range of an electro-optical sensor employing the heated detector and 1.7 to 2.0 times higher for an electro-optic sensor operating at 20 degrees C, compared to a sensor employing a standard silicon photo-conductor. An electro-optical system incorporating the new device can realize a significant performance increase and/or realize a significant reduction in the system aperture size (and related packaging parameters like weight, volume, etc.) while maintaining parity performance with similar systems that do not use the new detector. The paper describes the device and presents laboratory and field test results that testify as to the performance improvement that was achieved. These test results, for devices operating between -54 deg C and +100 deg C show that the heated detectors have significantly higher performance than conventional silicon detectors operating in the same environments. The advantages of using these devices in place of conventional detectors are also covered.
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James A. Harder, James A. Harder, Michaelene W. Sprague, Michaelene W. Sprague, } "Temperature-insensitive silicon photoconductor", Proc. SPIE 7482, Electro-Optical Remote Sensing, Photonic Technologies, and Applications III, 74820L (30 September 2009); doi: 10.1117/12.835861; https://doi.org/10.1117/12.835861

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