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12 November 2001 Proposed two-color HgCdTe focal plane array
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Recently there has been considerable interest in two-color focal plane arrays (FPAs), particularly in mercury cadmium telluride. Single-color FPAs provide only the signal from the target, not its emissivity and temperature separately. The schemes that have been implemented for two-color FPAs involve two bumps per pixel, and two back-to-back diodes in four different layers, which are technologically challenging. We propose a simple scheme that requires only one bump per pixel, in a material that is not a heterostructure, and can be grown by liquid phase or molecular beam epitaxy. The two different cutoff wavelengths are obtained by implanting two different junction depths in a n+-on-p configuration. Since the n+ layer does not contribute, because of the Moss-Burstein shift, the different diodes correspond to different surface composition values, xs1 and xs2, in the graded p-type epilayer. The precise cutoff wavelengths can be chosen by appropriate slope s of the composition in the epilayer. For the purpose of radiometry it is not necessary that the two cutoff wavelengths should differ by large amounts: even 0.3 mm is sufficient - easily achievable, with reasonable junction depths. The two colors could form a checkerboard pattern across the FPA.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vikram Dhar and Vishnu Gopal "Proposed two-color HgCdTe focal plane array", Proc. SPIE 4454, Materials for Infrared Detectors, (12 November 2001);


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