High performance LWIR detectors are highly needed. In order to image from long distance, it is important that imagers have high sensitivity, high resolution, and very low dark currents. This leads to technical goals of having low noise, low dark current in small size pixels in large arrays. While saturated performance levels of traditional systems based on bulk semiconductors have not quite met the requirement of applications, it is expected that novel quantum systems will bring new development stage for infrared imagers.In recent years, Type-II InAs/GaSb superlattice (T2SL) has experienced significant development, from theoretical modeling, material growth to device processing and packaging. Performance of LWIR detector based on T2SL has become comparable, even better than that of HgCdTe. However, LWIR T2SL devices have been shown to be limited by surface leakage, especially at lower operating temperature.This proposed effort will investigate gating of Type-II photodiodes as a means to suppress this bottle neck of T2SL technology. The ultimate goal of this project is to develop an effective method to completely suppress the surface leakage current in LWIR type-II superlattice photodiodes that is compatible with the development of high performance gated FPAs in Phase II.
Potential NASA Commercial Applications: (Limit 1500 characters, approximately 150 words) LWIR is also of special interest to NASA for planetary observation missions. The LWIR wavelength region is an ideal wavelength to look back at the earth from space and accurately map minute variations in the surface and/or atmospheric temperatures. It is even possible to use simultaneous measurements from two different LWIR wavelengths (a two-color camera) to help isolate the surface temperature from that of the atmosphere. This same LWIR technology can also be readily applied for observation of other planets.
Potential NON-NASA Commercial Applications: (Limit 1500 characters, approximately 150 words) IR imaging sensors also find their use in commercial applications such as deep-space astronomy, commercial satellite imaging, geophysics, geology, remote environmental (pollution) IR sensing, law enforcement, search and rescue, firefighting and emergency response. For its part, the Optoelectronics Industry Development Association estimates that the current infrared imaging market for military and law enforcement applications is about US$3 billion. The development of high performance LWIR imagers with higher operating temperature has the potential to significantly reduce the operational cost of these sensors and thus potentially open up new lower cost commercial applications.
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) Infrared Optical/Photonic (see also Photonics) Radiometric Thermal Imaging (see also Testing & Evaluation)
