TOPIC 1.3.4 Infrared Detectors: Demonstration of Dual-Band SWIR/MWIR Mini-Arrays and FPAs Based on Type-II Superlattices

High performance single-band focal plane arrays (FPAs) are sometimes unable to discriminate a target from its background when they present similar infrared radiation, at a given wavelength, which may occur even if the temperatures of the objects are different. Dual-band FPAs offer an additional wavelength that allows easy identification in such circumstances, and can provide additional functionalities by incorporating active and passive imaging capabilities in a single all-in-one camera. Current FPAs (eg. HgCdTe or Quantum Well Infrared Photodetectors) face fundamental and technological challenges when aiming for a hybrid active/passive imaging. InAs/GaSb/AlSb Type-II superlattices have been proposed as a viable technology and have already shown equivalent or better performance compare to the other state-of-the-art infrared detection material systems in single-band detectors. In this project, we propose to continue the development of Type-II superlattices with Phase I demonstrating dual-band mini-arrays based on Type-II superlattices, with equivalent performances as the state-of-the-art single-band devices in the Short-wavelength Infrared (SWIR) and Mid-wavelength Infrared (MWIR). This phase of the project will aim to understand how to manipulate the band structure of the superlattice through theoretical investigations, followed by experimental realization through Molecular Beam Epitaxial growth, and finally, fabricating and characterizing the functional dual-band mini-arrays that sense in the SWIR and MWIR. This will provide the necessary data and designs for Option II and Option III. The Phase I of the project will focus on fabrication and delivery of dual-band SWIR/MWIR miniarrays. Initial detectivity optimization such that the detectors perform near their theoretical limits, that is, the detectors are background limited infrared photodetectors (BLIP), will also be studied. Concurrently, the fabrication process for mini-arrays will be investigated and suitable etch-stop materials and substrate removal techniques will be developed. Following the successful demonstration of high detectivity backside illuminated mini-arrays, the effort will focus on minimizing the pixel size for future development of high uniformity/operability focal plane arrays. Finally, the effort will focus on development of high uniformity/operability 640×512 focal plane arrays (optional). The focal plane array will be an all-in-one single-aperture, co-registered dual-band sensor with channels for SWIR and MWIR hybridized to a readout integrated circuit (ROIC), and ready for system integration and testing.