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 5-14 um detection. Photodetector 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 60%.
Potential NASA Commercial Applications: (Limit 1500 characters, approximately 150 words) Commercial applications applicable to NASA include remote chemical sensing and IR imaging arrays for deployment on remote vehicles. The LWIR data is valuable for object discrimination when tracking targets in space or performing astronomical observations. The Type-II superlattice developed here operates at ambient temperatures or under passive cooling, allowing for the possible replacement of extrinsic Si-based photodetectors which require more cumbersome cryogenic cooling. This in turn reduces the weight and volume overhead required for supporting systems on space-based or portable platforms. Chemical plumes could be analyzed and identified based on their infrared absorption signatures. Thermal imagers can be applied to geologic and atmospheric studies, for either earth based or extraterrestrial projects. Data on weather patterns or geothermal activity could then be collected. At these long wavelengths objects can also be spotted through fog or dust, which would normally obscure visible light wavelengths.
Potential NON-NASA Commercial Applications: (Limit 1500 characters, approximately 150 words) Non-NASA Commercial Applications includes pollution monitoring, nondestructive testing, medical diagnostics, and target tacking. For civilian medical use thermal imaging can be applied to diagnosing certain cancers based on temperature anomalies at the skin surface. Search and rescue operations are also aided with this technology in that the ability to detect heat sources provides a great and immediate visual contrast when viewing vast areas of land or seascape. Similarly military and defense can also benefit from this technology. Standard night-vision systems rely on image intensifiers which merely amplify the available visible light for the user. Camouflaging can still fool these types of vision systems. However, thermal imaging that LWIR arrays can provide adds a higher level of capabilities. Potential enemies can more easily be spotted by the heat signature that is emitted by their bodies or recently discharged weapons. Lingering heat patterns can also reveal if a room or vehicle has been recently occupied.
Technology Taxonomy Mapping: (NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.) Detectors (see also Sensors) Image Capture (Stills/Motion) Thermal Thermal Imaging (see also Testing & Evaluation)
