7 May 2010 Performances of AlGaN-based focal plane arrays from 10nm to 200nm
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The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. Camera based on this alloy present an intrinsic spectral selectivity and an extremely low dark current at room temperature. We present here an extension from near UV (360 nm-260 nm) to deep UV (10 nm-200 nm) in a packaging common to the SWIR supply chain. It concern both readout circuit and camera electronics. Such camera are now available for on UV optical budget evaluation. The vacuum UV wavelengths are a very difficult range for detection due to the strong interaction of light with materials. Nevertheless, such wavelengths are of prime importance for solar observation. We present a prototype of focal plane arrays to extend the range of detection from near UV to deep UV. It is based on 320 x 256 pixels of Schottky photodiodes with a pitch of 30 μm. AlGaN is grown on a silicon substrate instead of sapphire substrate only transparent down to 200 nm. After a flip-chip hybridization, silicon substrate is thinned and removed by dry etching. The use of a honeycomb structure straightens the membrane after hybridization and allows the membrane integrity. The results show that the dry etching process doesn't affect the readout circuit properties. The dark current is negligible and the measured noise is the readout noise due to the large capacitance of the photodiode. The spectral responsivity of this focal plane array presents a quantum efficiency from 10% to 20% from 50 nm to 290 nm after the removing of the highly doped contact layer.
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J.-L. Reverchon, S. Bansropun, J.-P. Truffer, E. Costard, E. Frayssinet, J. Brault, J.-Y. Duboz, A. Giuliani, and M. Idir "Performances of AlGaN-based focal plane arrays from 10nm to 200nm", Proc. SPIE 7691, Space Missions and Technologies, 769109 (7 May 2010); doi: 10.1117/12.853947; https://doi.org/10.1117/12.853947

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