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Metamorphic Buffer Layer Growth for Bulk InAs(x)Sb(1-x) LWIR Detectors



The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 5.4.c.(8) of the solicitation.

OBJECTIVE: Development of metamorphic buffer layers on commercially available IIIV substrates (GaAs or GaSb) for the growth of high quality III-V BULK material based long-wavelength infrared (LWIR) nBn detectors.

DESCRIPTION: Advantages from improved uniformity and increased process yields of III-V detector materials are being realized in the mid-wavelength infrared (MWIR) via device structures that incorporate a unipolar barrier layer. MWIR devices incorporating these barrier structures are now becoming commercially available in high operating temperature (HOT) and HD formats.1 The devices employ an Al As(x) Sb(1-x) based alloy for the unipolar barrier to block majority carriers and surface leakage current, as well as suppress generation-recombination current.2 Incorporation of narrow gap InAs(x)Sb(1-x) in a unipolar barrier architecture with an Al(x)In(1-x)Sb barrier layer could enable realization of these advantages for bulk long-wavelength infrared (LWIR) detectors.

Unlike strained layer superlattice (SLS) structures, bulk InAs(x)Sb(1-x) has the advantage of high, isotropic hole mobility. As such, it presents an avenue to achieve longer carrier diffusion length resulting in high quantum efficiencies with n-type device architectures, such as the nBn. Another advantage of InAs(x)Sb(1-x) is the potential to produce bulk material with a spectral cutoff out to nearly 12.5 ?m. This was revealed in a recent study that showed a narrower than previously thought band gap for InAs(x)Sb(1-x). The study attributed the narrow band gap to large band bending for the InAs(x)Sb(1-x) alloy.3 Incorporating narrow gap InAs(x)Sb(1-x) into a unipolar device architecture will require the identification and optimization of a metamorphic buffer layer to transition from a commercially available substrate to the lattice constant of the InAs(x)Sb(1-x) detector material. InAs(x)Sb(1-x) absorber layers have been grown on GaSb by Wang et al.4, and GaAs by Lubyshev et al. 5 utilizing various metamorphic buffer layer schemes with encouraging results.

The relative simplicity of processing detectors based on the nBn device structure will enable rapid adoption by commercial foundries. Commercial III-V foundries including material growers should be able to use these recipes to develop advanced high resolution LWIR FPAs with enhanced performance suitable integrate with U.S. Army and DoD systems giving the tremendous advantage to U.S. Warfighters. Commercial applications of devices based on bulk InAs(x)Sb(1-x) include medical diagnostics and therapeutics, chemical and pollution sensing, materials processing, industrial process monitoring, food safety monitoring, aircraft anti-missile warning/protection and combustion diagnostics for high efficiency power generation. DoD applications include infrared countermeasures (IRCM), detect/locate hostile fire, detect/negate hostile imagers, sensors for persistent surveillance, helicopter landing during brownout, missile warning, and detection of explosive and chemical warfare agents.

PHASE I: Develop a plan to identify the best substrate and metamorphic buffer material combination(s) to reduce stress and/or strain in subsequently grown bulk InAs(x)Sb(1-x) layers. Following identification of the potential substrate/metamorphic buffer layer material system(s), develop a systematic material growth and characterization plan. The characterization plan should include techniques capable of imaging individual defect types as well as assessing the overall density of defects in the InAs(x)Sb(1-x) layer. It is strongly encouraged that the work be conducted in collaboration with a commercial epitaxy vendor to increase the potential for commercialization of bulk LWIR devices based on this effort. Demonstrate growth of bulk InAs(x)Sb(1-x) with a spectral cutoff > 11.5µm on a commercial substrate, and provide a sample to the Army for characterization.

PHASE II: Optimize the growth of the metamorphic buffer layer to minimize the density of active defects in the bulk InAs(x)Sb(1-x) to demonstrate LWIR nBn devices with a spectral cutoff > 11.5µm. Demonstrate growth of nBn device structures incorporating the optimized metamorphic buffer layer and bulk InAs(x)Sb(1-x) absorber. Collaboration with commercial infrared imager foundries for device structure development and characterization is strongly encouraged to support the commercialization of the bulk InAs(x)Sb(1-x) detector material.

PHASE III DUAL USE APPLICATIONS: The contractor shall pursue commercialization of the technology developed in Phase II for potential commercial uses in such diverse fields as law enforcement, rescue and recovery operations, maritime and aviation collision avoidance sensors, medical uses, homeland defense, and other infrared detection and imaging applications. The technology will be developed as product or growth recipes that can be licensed or transferred and utilized with limited expertise, irrespective of the commercialization route. Commercial III-V foundries including material growers should be able to use the product or recipes to develop advanced high resolution LWIR FPAs with enhanced performance suitable to integrate with U.S. Army and DoD systems. Successful demonstration of this technology will lead to insertion in systems for next generation forward looking infrared detectors, and provide important leap ahead wide area persistent surveillance systems and infrared search and track capabilities for the Warfighter including Army tactical systems like the Javelin. The successful development of high uniformity LWIR nBn detectors based on III-V material will immediately improve the performance of systems requiring advanced high performance infrared sensors by reducing size, weight, and power consumption requirements as well as cost.


    • Y. Karni, E. Avnon, M. B. Ezra, E. Berkowitz, O. Cohen, Y. Cohen, R. Dobromislin, I. Hirsh, O. Klin, P. Klipstein, I. Lukomsky, M. Nitzani, I. Pivnik, O. Rozenberg, I. Shtrichman, M. Singer, S. Sulimani, A. Tuito, E. Weiss, Proc. SPIE 9070, Infrared Technology and Applications XL, 90701F (2014)


    • S. Maimon, G. W. Wicks, Appl. Phys. Lett. 89, 151109 (2006)


    • SP Svensson, WL Sarney, H Hier, Y Lin, D Wang, D Donetsky, L Shterengas, G Kipshidze, G Belenky Phys. Rev. B 86, 245205 (2012)


    • D. Wang, D. Donetsky, G. Kipshidze, Y. Lin, L. Shterengas, G. Belenky, W. Sarney, S. Svensson, Appl. Phys. Lett. 103, 051120 (2013)


  • D. Lubyshev, J. M. Fastenau, Y. Qiu, A. W. K. Liu, E. J. Koerperick, J. T. Olesberg, D. Norton Jr., N. N. Faleev, C. B. Honsberg, Proc. of SPIE 8704 870412-1 (2013)

KEYWORDS: Infrared detectors, InAs(x)Sb(1-x), long wavelength infrared (LWIR), material growth, metamorphic buffer layer, nBn, III-V antimony based material, unipolar barrier

  • TPOC-1: Neil Baril
  • Phone: 703-704-4900
  • Email:
  • TPOC-2: Sumith Bandara
  • Phone: 703-704-1737
  • Email:
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