Long wave HgCdTe staring arrays at Sofradir: from 9 μm to 13+ μm cut-offs for high performance applications

Abstract

Today, end users require Long Wave (LW) staring arrays to develop new compact IR cameras, and Very Long Wave (VLW) staring arrays to develop high performance applications with broadband detection up to more than 13μm. HgCdTe is the only available material to answer these needs with the same production line. Based on its HgCdTe Liquid Phase Epitaxy (LPE) process that has proven its maturity and reproducibility over the last thirteen years, with for example more than 14,000 288×4 IRFPAs already delivered worldwide, SOFRADIR has been offering for several years 320×256 LW detectors with a cut-off wavelength tuned between 9μm and 12μm depending on the required application. Based on that experience, two new LW HgCdTe products have been developed and are offered since beginning of 2005. For compact LW FLIRs, SOFRADIR offers the VENUS-LW: a higher resolution 25μm pitch 384×288 IDDCA with 0.5W micro cooler, with a cut-off between 9μm and 10μm for a spectral band pass fully satisfying the imagery requirements and for an operational temperature between 77K and 85K (thus enabling the use of a compact low power micro cooler). The manufacturing of this detector relies on the standard HgCdTe production process with the latest uniformity improvements. Following a similar approach and for VLW applications such as spectroscopy or broadband low flux applications, an improved HgCdTe material with optimized LPE and PhotoVoltaic (PV) detector processes, has been developed by SOFRADIR and LETI LIR for cut-off wavelengths above 12μm below 60K, enabling to have very low dark currents compatible with very low flux applications. These high performance low dark current detectors are offered with a standard 30μm pitch 320×256 readout circuit, integrated with a 1 Watt split Stirling cycle cooler enabling to reach the 50K range with very short cool down times. The performances of these new LW and VLW IR detectors are presented in this paper as well as the development trends for LW detectors at SOFRADIR.