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Developments in Reduced Pixel Geometries with MOVPE Grown MCT Arrays
The fabrication of high performance infrared detectors using mercury cadmium telluride (MCT) grown on GaAs substrates by Metal Organic Vapour Phase Epitaxy (MOVPE) is now an established mature production process at Selex ES. Recent years have seen a substantial reduction in MCT pixel sizes, driven by system requirements for increased resolutions, lower power consumption and reduced costs. From initial devices with 30μm pixels, previous developments have produced MOVPE grown MCT arrays of 24μm, 20μm and 16μm pixels with response in short, long, mid and dual wavebands (SWIR, LWIR, MWIR and DWIR). High definition (HD) format and multi-megapixel arrays of 12μm MWIR pixels have also been produced using MOVPE grown MCT. The mesa structure of MOVPE grown MCT pixels inherently controls optical scattering, inter-pixel cross-talk, carrier diffusion and other blurring defects to negligible levels. This allows the goal for pixel size reduction to ultimately be determined by optical diffraction and Nyquist- Shannon sampling criteria alone. This paper discusses the development of a new MCT detector at Selex ES, introducing the next generation of small pixels on an 8μm pitch. Transition to smaller silicon design rules has enabled the pixel size reduction in the read-out integrated circuit (ROIC) to be achieved with minimum sacrifice of storage capacity. The ROIC has a completely digital control with on-chip digital generation of photodiode bias voltage. Low power proximity electronics providing a fully digitised output have been developed to ease interface with the detector. Characteristics of the pixel design together with measured performance of the detector and its application to infrared sensor development, including updates of standard definition (SD) products to HD and better performance, will be addressed.
McEwen Kennedy, Jeckells David, Bains Sudesh
Paper for Seminar/Symposium/Conference
SPIE 2015 - Infrared Technology and Applications conference (20-24 April 2015, Baltimore, Maryland, USA)
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