Progress in HgCdTe homojunction infrared detectors

SOFRADIR/LIR HgCdTe homojunction infrared (IR) detector technology has already demonstrated its high maturity level by delivering more than 1000 s and third generation detection dewar assemblies. This specific HgCdTe photovoltaic technology proves high performance including low fixed pattern noise and high yield. This is due to the high impedance photodiode (including the longwave band) obtained thanks to the high-duality HgCdTe material used and the planar homojunction technology based on a very efficient passivation and ion implantation. Furthermore, much progress has been made in reducing IR detector cost and proposing new detector dewar assemblies. The efforts are mostly dedicated to the increase in HgCdTe wafer dimensions and yield for large staring arrays, and to the increase in IR detector operating temperature in order to reduce dewar and cooler assembly cost as well as cooler input power. Thus, Sofradir offers HgCdTe staring arrays operating at full performance at over 90 K for 8-10 mu m wave band and at around 130 K for 3-5 mu m wave band. Based on existing detector results, the main technological progress is presented. In particular, a 320 x 240 InfRared Focal Plane Array (IRFPA) is presented in 3-5 mu m at 130 K and in 8-10 mu m with the same performance at 80 and 90 K. Those new staring arrays provide very high thermal sensitivity (less than 10 mK) and low fixed pattern noise. A 5 cm long linear array using a special butting hybridization technique and allowing zero defect at the joints is introduced. It consists of a one 1500 x 1 linear array sensitive in the 3-5 mu m wave band. The same format, sensitive in the 8-12 mu m wave band, is also presented. Finally, future trends are discussed. (C) 1988 Published by Elsevier Science B.V. All rights reserved.