T2SL technology developments in MWIR band operating at a high temperature

Forty years of heritage have shaped LYNRED into a leading provider of advanced infrared detectors for defense, space, and civilian applications As a global leader, LYNRED delivers high-quality II-VI, III-V, and bolometer-based infrared detectors from near to far infrared. Two trends have been identified in the infrared range, the increase in operating temperature and the reduction of the pixel pitch. For the past 15 years, III-V technologies have shown an increasing interest as a means to address both challenges. At LYNRED, these technologies enable the development of Short Wave InfraRed (SWIR) and Mid-Wave InfraRed (MWIR) detectors for ground applications. The latter is achieved using both bulk InAsSb material and the type-II superlattices (T2SL), depending on the wavelength range of interest. Building on LYNRED’s knowhow, T2SL material is under development to offer a complete product line covering the full MWIR range, from 3.5 up to 5.1 μm.

Many challenges must be addressed for the two formats of focal plane arrays (FPAs): VGA with a 15 μm pitch and SXGA with a 7.5 μm pitch. Electrical and optical crosstalk, as well as image quality and stability, are among the primary concerns for detectors with such small pixel pitches. To achieve industrial-scale production of infrared FPAs, technological developments are required at every stages: epitaxy, detector array processing, flip-chip integration, and back-end processing. Another key element is the in-house design of the Read-Out Integrated Circuit (ROIC) to meet our customers' needs.

We review the latest developments at LYNRED on T2SL technology, in terms of operability, residual fixed pattern noise (RFPN) and Modulation Transfer Function (MTF) optimizations.