Low reflectance, blinded HgCdTe pixels would allow the effects of drifts in the supply voltage and operating temperature to be accounted for when trying to resolve very faint objects. This paper describes the progress of an ESA / Leonardo contract in developing such a layer. The structure chosen offers significant levels of blocking for the masked pixels as well as minimal reflection to prevent optical cross-talk to neighbouring pixels.
Having established production capacity for high resolution, small pixel Mid Wave Infra-Red (MWIR) devices down to 8μm; this paper discusses the latest developments at Leonardo UK with 12μm MWIR-LWIR Dual Waveband Infra-Red (DWIR) high-performance infrared detectors, grown by Metal Organic Vapour Phase Epitaxy (MOVPE) on GaAs substrates. As with the 30μm, 24μm and 20μm mesa pixels that Leonardo UK pioneered during the early 2000’s, the 12μm devices use a “back-to-back” diode arrangement, whereby the waveband is selected by changing the bias polarity across the diode stack; thus ensuring spatial coherence between the two wavebands. The increased thickness of DWIR MCT compared to single-band material makes manufacturing the mesa structure, in order to control inter-pixel crosstalk increasingly challenging with smaller pixel pitches. Previous publications by Leonardo UK presented results of 12μm DWIR technology on a 24μm Readout Integrated Circuit (ROIC), allowing only 25% of the pixels to be assessed; in this paper, we discuss results of this material on a 12μm ROIC, enabling assessment of 100% of the pixels. Low defects together with near Background Limited Infra-red Photodetector (BLIP) performance demonstrates significant progress towards the manufacture of higher resolution, lower cost DWIR devices by Leonardo UK.
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