Simulation of Small-pitch High-density Photovoltaic Infrared Focal Plane Arrays

Abstract

Scanning and starring photovoltaic infrared focal plane arrays (PV IRFPAs) based on ternary alloys Hg1-xCdxTe (Whicker, 1992; Triboulet & Chatard, 2000; Baker & Maxey, 2001; Norton, 2002; Kinch, 2007) and binary compound InSb and its alloys (Glozman et al., 2006) are considered as the most sensitive, flexible and perspective for detection of infrared radiation in spectral ranges 1.5-2.7 ┤m Short-Wave IR (SWIR), 3-5.5 ┤m Mid-Wave IR (MWIR), 8-14 ┤m Long-Wave IR (LWIR) and longer than 14 ┤m Very Long-Wave IR (VLWIR). Those FPAs are updated and improved continuously and move gradually from linear arrays such as 288×4 (TDI); 480×(4-8) (TDI); 768×8 (TDI) pixels to mid-format (sub-TV and TV) including but not limited 64×64; 320×256; 384×288; 640×512 pixels and finally to megapixel format (High Definition TV) like 1280×768; 1280×1024 pixels and more. Nowadays all manufacturers offer LWIR PV FPA with peak wavelength ┣p ≈ 8.5±0.5 ┤m. It means that scanning thermal imagers (TI) based on old LWIR photoconductive (PC) linear arrays (┣p ≈ 11 ┤m) covers 8-14 ┤m atmospheric “window” of transparency totally whereas TI based on LWIR PV FPA with ┣p ≈ 8.5±0.5 ┤m covers left (shorter) part of that “window” only. As the result TIs based on LWIR PC linear arrays (┣p ≈ 11 ┤m) allow adequate visualizing of cold landscape (scene) with temperatures as low as minus 60 0C. Thermal Imagers based on LWIR PV FPA with ┣p ≈ 8.5±0.5 ┤m can visualize adequately cold landscape at scene temperatures higher than minus 30 0C (even higher than minus 20 0C). Full replacement of scanning type TI by starring type TI will take place when extended LWIR PV FPA with ┣p shifted to 10-11 ┤m at Top=80-100 K will become affordable. Megapixel high performance IRFPA having extended spectral covering with ┣p=10-11 μm at Top=80-100 K could be preferable to create future TI systems. Increasing of array format along with improvement in performance is general development trend in IRFPA technology. It is accompanied inevitably by decreasing of pixel size and pixel pitch to minimal size reasonable from point of view of infrared physics to provide the best resolution and producing comfortable imaging with electro-optic (EO) system. Pitch in small-pitch PV IRFPA can be equal to from 10 ┤m to 20 ┤m. PV arrays based on InSb and its alloys or Hg1-xCdxTe alloys are fabricated often on single layer (substrate) that is common for all pixels of array.