Scientists at the U.S. Army Research Laboratory (ARL) and Stony Brook University have developed a new synthesis process for low-cost fabrication to use the semiconductor InAsSb in high-performance IR cameras. The newly developed infrared detector is for the longest wavelengths (10 micron). The best materials for the IR camera light-sensors currently utilize the very expensive compound semiconductor HgCdTe, that is only used in such IR detectors. However, InAsSb is much more common and is used in DVD players, optoelectronics, and cell phones.
ARL scientists realized material had to be undistorted by strain
According to the ARL scientists, the key to the breakthrough was the realization that the material had to be undistorted by strain to see at 10 microns.
InAsSb is deposited onto a substrate material which has a smaller spacing between the atoms. This size atom-scale mismatch had to be managed well to get the light-sensitive material to work. The scientists used a somewhat common GaAs substrate with an intermediate layer of GaSb to trap most of the defects caused by the atomic-scale mismatch.
In addition being much less expensive to produce, the design works on GaAs substrates, which can be made into larger sizes to allow more sensors on individual wafers. This larger size capability translates to additional cost savings. Furthermore, the process that they developed could be completed at commercial foundries, at a greatly reduced cost. The research points the way to a lower cost night vision solution for soldiers. The details of the research were published in the Journal of Applied Physics.
W. L. Sarney, S. P. Svensson, Y. Xu, D. Donetsky, and G. Belenky , Bulk InAsSb with 0.1 eV bandgap on GaAs, Journal of Applied Physics 122, 025705 (2017). doi.org/10.1063/1.4993454