The tri-service Vital Infrared Sensor Technology Acceleration (VISTA) program rapidly matured III-V semiconductor epitaxy to produce tactically viable detectors using Type II Superlattice (T2SL) structures. The T2SL material system allows tunable band gaps for creating lattice-matched heterojunction devices. Heterojunction devices are integral to suppressing sources of dark currents, such as internal Shockley Reed Hall (SRH) and device surface currents. Once the VISTA program demonstrated that T2SL detectors offered competitive performance to traditional indium antimonide (InSb) detectors at an operating temperature 40K to 50 K higher, many opportunities emerged. This elevation in operating temperature provides two benefits to infrared (IR) sensors. The first is to miniaturize the integrated Dewar-electronicscooler assembly (IDECA) such that it can support small aerial vehicle and soldier mounted sensors. The second is to increase the mean time to failure (MTTF) of an existing InSb IDECA. To benefit from T2SL higher operating temperature (HOT) detectors, the overall cost of the IDECA must be competitive with InSb. This drives a manufacturing capability that is equivalent to InSb. At the L3 Space and Sensors Technology Center (L3 SSTC), the III-V detector foundry processes 125 mm diameter InSb wafers. The development of 125 mm diameter T2SL detector wafers started with the gallium antimonide substrates. The greater size and weight of these substrates required extra care to avoid breakage. Leveraging the learning reported from the silicon industry, we developed a specification for the substrate thickness and edge bevel to provide a robust platform for wafer processing. Next, we worked with commercial III-V epitaxy suppliers to develop multi-wafer growth capability for 125 mm diameter substrates. The results of this effort, funded by the Office of the Secretary of Defense (OSD) Defense-wide Manufacturing Science and Technology (DMST) program through the Army Night Vision and Electronic Sensor Directorate (NVESD), we were able to improve focal plane array (FPA) yield from virtually zero to InSb manufacturing levels.
David Forrai, Robert Jones, Michael Garter, Yajun Wei, Steven Allen, and Laura Couch, "Transitioning large-diameter Type II Superlattice detector wafers to manufacturing," Proc. SPIE 10624, Infrared Technology and Applications XLIV, 106240L (Presented at SPIE Defense + Security: April 17, 2018; Published: 21 June 2018); https://doi.org/10.1117/12.2311515.
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