We propose to develop Multi-Spectral VLWIR Focal Plane Arrays for Exo-atmospheric Kill Vehicle (EKV) Seekers. The innovative features are: 1) Detector structures are grown on Type II Strained Layer Superlattices (SLS) material in a Molecular Beam Epitaxial (MBE) reactor by using Migration Enhanced Epitaxial Technique. 2) Detailed analysis is conducted by using 8- band k.p. model to design SLS structures for Very-Long Wavelength (24um) range. 3) Co-Located SLS Structures are grown for VLWIR1 (10-16um) and VLWIR2 (16-24um) waveband ranges with Al(x)Ga(1-x)As/InAs SLS layers. 4) The readout circuitry and the interconnect scheme are designed to detect the two waveband signals in a simultaneous fashion during each frame. 5) 320 x 256 element Dual Band Detector array is integrated with high speed and low noise ROIC arrays. 6) The ROIC device is designed to operate at 77K, since the SLS technology is capable of producing VLWIR detectors to operate at a comparatively higher operating temperature of 77K. Si-based VLWIR focal plane array, on the other hand, requires extra design features to cool the detector array and to operate the ROIC array at very low temperature level of 20K with the associated cost and design complexities. 7) SLS structures are grown on GaSb substrate and the detectors are fabricated with Silicon-Nitride passivation. These structures are expected to produce higher radiation-hardened devices as compared HgCdTe wafers grown on CdZnTe substrate and fabricated with Silicon Diode passivation. High Performance Al(x)Ga(1-x)Sb/InAs detectors were already fabricated and tested for SWIR(1-3um) waveband. The results showed: Detectivity (cm-Hz (1/2)/W) = 1E12 at 77K, 1.4E11 at 250K, 2E10 at 300K and quantum efficiency (n) = 72% at 300K. During Phase 1, the growth of Al(x)Ga(1-x)Sb/GaSb SLS structures will be optimized and wafers will be grown for VLWIR1 (10-16um) and VLWIR2 (16-24um) wavebands and detector fabrication will be initiated. Also during Phase 1, methods to improve the speed and lower the noise of the ROIC will be investigated. During a potential Phase 2, 4 x 4 element Co-Located Dual Band Detector Arrays will be fabricated and integrated with high speed, low noise ROICs. Also during Phase 2, 320 x 256 element VLWIR focal Plane Arrays will be designed. During a potential Phase 3, IR Camera will be designed and built with Dual Band VLWIR focal plane arrays to operate at 77K temperature levels. ADT is presently working on a Phase 1 SBIR Contract for MDA entitled "Co-located Dual Band (VLWIR1/VLWIR2) Focal Plane Arrays for Space Applications". Under the on-going project, Co-located Dual Band Detector Arrays are being developed on SLS material to cover VLWR1 (10-16 um) and VLWIR2 (16-24 um) wavebands. Under the proposed project, Dual VLWIR detector arrays will be integrated with high speed, low noise ROICs. Anticipated Benefits/Commercial Applications: The proposed approaches will give state-of-the-art Multi-color VLWIR detectors for advanced missile seekers High performance, Multi-spectral VLWIR focal plane arrays on low cost, large area substrates is a basic requirement for several programs in the commercial and military sectors. The growth of SLS structures on GaSb substrates allows the development of FPAs with mature fabrication methods and uniform material properties. The large size of the substrate will allow the development of very large format focal plane arrays. The military applications include: 1) EKV missile seekers, 2) airborne remote sensing 3) the combined threat warning and reconnaissance applications, 4) target discrimination, 5) counter-measure rejection and 6) clutter rejection. The commercial applications include: 1) medical imaging 2) night vision equipment for law enforcement agencies and for navigation, 3) environmental monitoring and 4) process control for manufacturing.
Keywords: Dual Band (VLWIR) Detectors, Superlattices, Co-Located Dual Band, Simultaneous Detection, High Speed, Low Noise ROIC, Radiation-Hardened Array
