High-Detectivity Type-II Superlattice Detectors for 6-14 um Infrared Applications

SVT Associates proposes an novel type II superlattice structure to extend the cutoff wavelength and CBIRD SL photo diode structure with unipolar barriers to suppress dark current of SL detectors grown on GaSb substrate. This InAs/GaSb superlattice material system is capable of infrared detection in MWIR/LWIR spectral range, depending on layer thickness of each superlattice period. The goal of this program is to develop high performance type II SL based FPA for 6-14 um detection. Photo detector arrays using this material are of great interest to the NASA for various applications including, in particular, imaging and optical detection, and object discrimination when tracking targets in space or performing astronomical observations. These LWIR photo detectors can also find application to infrared-based chemical identification systems and terrestrial mapping. Applying the dark current suppression and cutoff wavelength extension process to the type II superlattice detectors should result in higher operating temperature, extended cutoff wavelength, and improved quantum efficiency, all important factors that should significantly enhance FPA operation. We intend to characterize the positive effects of proposed techniques in Phase I. In Phase II we will refine the techniques to realize passive-cooled high-performance LWIR FPAs with quantum efficiency larger than 50%.