Materials Development for Long Wave Infrared Focal Plane Arrays with Type II InAs/GaSb Superlattices

In the proposed effort, SK Infrared LLC (SKI), a spin-off from the Krishna INfrared Detector (KIND) laboratory at the University of New Mexico (www.chtm.unm.edu/kind), in collaboration with Raytheon Vision Systems (RVS) and Intelligent Epitaxy Inc (Intelliepi) is proposing a systematic study with the following two objectives. (a) Optimization of the epitaxial growth parameters to reduce dark current noise, decrease growth defects, improve uniformity and increase device reliability and reproducibility (in collaboration with Intelliepi) (b) Explore novel detector architecture that leverages the bandgap engineering flexibility of the superlattice absorber combined with the barrier engineering capability of the 6.1 semiconductor family and integrate them into FPAs (in collaboration with RVS) As a part of this effort, the advances made in the improving the epitaxial growth procedure will be transitioned to Intelliepi and advances in the heterostructure design and FPA fabrication will be transitioned to RVS. The KIND lab has recently purchased a $1.35M Veeco Gen-10 MBE reactor with Sb and As valved cracker source capable of highly uniform growth on 3-inch wafers. SKI will have access to this reactor through the user facility at the Center for High Technology Materials (CHTM). In particular, we will explore a double-unipolar barrier design called PbIbN. The double-barrier heterostructure design (PbIbN) belongs to the family of band gap engineered SLS architectures, such as nBn , M-structure , W-structure , and complementary barrier infrared detector (CBIRD) . The improved performance of these SLS devices over the homojunction SLS detectors is credited to reduction in dark current by use of current blocking layers either in conduction or valence bands which reduce one or several dark current components. The PbIbN design further reduces noise in SLS-based detectors, since it contains wider bandgap potential barriers in both valence and conduction bands. In PbIbN detector design, the electron blocking (EB) layer sandwiched between P contact layer and absorber region blocks the minority carrier diffusion (electrons) current from P contact layer into the absorber region. Similarly the hole blocking (HB) layer blocks minority carrier diffusion (holes) current from N contact layer into the absorber region. Moreover, the electric field drop across the active region is small as compared to a conventional PIN design since there is significant amount of field drop across the EB and HB layers, which have a wider band gap compared to the absorber region. This reduction in electric field leads to very small depletion region and hence reduction in the Schockley-Read-Hall (SRH) generation-recombination component of dark current. The tunneling currents are also reduced due to significant reduction in field drop. Thus the device can be made diffusion limited over wide range of operating temperatures, thereby improving the performance of the device.