The HgCdTe infrared detector technology developed by CEA-LETI and industrialized by Sofradir is mature and reproducible, and the n on p planar ion implanted diode junction formation, which is well mastered for lot of years, allows high yields to be achieved in production. Even if most of the devices produced today are FPAs with increasing complexities (megapixel) operating in MWIR bands, HgCdTe FPAs with longer and longer cut off wavelengths become more and more available.
Arrays of 384x288 with a pitch of 25μm are already available in production at Sofradir for LWIR bands (9-10μm & 11μm and operating temperature 77-85K & 70K respectively).
Improvement of both the material (with state of the art CdZnTe lattice matched substrates, state of the art HgCdTe epitaxial layers grown by liquid phase (LPE)), and of the photovoltaic detector process (improved dark current technology), have allowed FPAs with longer cut off wavelengths (VLWIR) to be fabricated.
These VLWIR (cut-off wavelengths in the 12-18μm range) dedicated to spectroscopy or broadband low flux applications operate at low temperatures around 50K and exhibit a very low dark current compatible with low flux applications.
In this paper we present the latest developments of VLWIR FPAs of TV/4 typical size (320x256, 30μm pitch, 18 μm cut-off) made in Defir (LETI-Sofradir joint laboratory).