A demonstrational thermal imaging LWIR camera system is described which is based on photovoltaic Pb_1-xSn_xSe-on-Si infrared sensor arrays. Epitaxial Pb_1-xSn_xSe layers, about 2 micrometer thick, are grown by molecular beam epitaxy onto 3 inch Si(111) substrates, and employing an intermediate CaF₂ buffer layer of only 2 nm thickness for compatibility reasons. Linear arrays with 256 pixels on 50 micrometer centers are fabricated in the layers with a batch photolithographic technique. Cut- off wavelength is about 10 - 10.5 micrometer at operating temperatures of 80 - 120 K, and quantum efficiencies greater than 60%. The sensors operate near BLIP. The read-out electronics chips contain, for each sensor, an integrator with a low noise JFET input transistor, correlated multiple sampling, and a sample and hold amplifier. They are wire- bonded to the sensor array. The JFET input transistors allow it to amplify from much lower source impedances (down to less than 10 kOhm) than with CMOS design without adding significant noise. Infrared sensors with lower impedances, operation at higher temperature, or sensors with longer cut-off wavelengths can therefore be used.

Date Published: 8 September 1995
PDF: 7 pages
Proc. SPIE 2552, Infrared Technology XXI, (8 September 1995); doi: 10.1117/12.218240

Published in SPIE Proceedings Vol. 2552:
Infrared Technology XXI
Bjorn F. Andresen; Marija Strojnik, Editor(s)