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Proceedings Paper

320 x 240 pixels quantum well infrared photodetector (QWIP) array for thermal imaging: fabrication and evaluation
Author(s): Jan Y. Andersson; Jorgen Alverbro; Jan Borglind; Per OF Helander; Henk H. Martijn; Mikko Oestlund
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Paper Abstract

Due to the well established GaAs material and processing technology QWIPs are viable candidates for high resolution (greater than 128 by 128 pixels), low cost LWIR (8 - 12 micrometer) focal plane arrays (FPAs). Usually n-doped AlGaAs/GaAs QWIPs are used since, at least to date, these have been shown to provide the highest performance. Fabrication and evaluation of 320 by 240 pixels QWIP arrays have also been done. The fabrication involves hybridizing GaAs chips consisting of detector mesas to specially designed CMOS readout chips. The hybridization is effected by indium bump flip-chip bonding. Optical coupling into the detectors is performed by using optimized, etched, two-dimensional gratings combined with GaAs substrate thinning down. The advantages of substrate removal are: (1) reduction of thermal mismatch between materials and thus permitting large array sizes, (2) enhancement of absorptance, and (3) elimination of optical cross-talk between pixels. The intended operating temperature range is 70 to 73 K, achievable by a miniature Stirling cooler. Excellent wafer uniformities resulting in responsivity uniformities of 3.3% across an array are found, and a temperature resolution NETD (noise equivalent temperature difference) equals 40 mK is achieved. Finally, the presence of fixed-pattern noise and its influence on the image performance are discussed.

Paper Details

Date Published: 13 August 1997
PDF: 9 pages
Proc. SPIE 3061, Infrared Technology and Applications XXIII, (13 August 1997); doi: 10.1117/12.280392
Show Author Affiliations
Jan Y. Andersson, Industrial Microelectronics Ctr. (Sweden)
Jorgen Alverbro, Industrial Microelectronics Ctr. (Sweden)
Jan Borglind, Industrial Microelectronics Ctr. (Sweden)
Per OF Helander, Industrial Microelectronics Ctr. (Sweden)
Henk H. Martijn, Industrial Microelectronics Ctr. (Sweden)
Mikko Oestlund, Industrial Microelectronics Ctr. (Sweden)

Published in SPIE Proceedings Vol. 3061:
Infrared Technology and Applications XXIII
Bjorn F. Andresen; Marija Strojnik, Editor(s)

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