We present in this study a theoretical and experimental investigation of the MWIR HgCdTe nBn device concept. Theoretical work has demonstrated that the HgCdTe nBn device is potentially capable of achieving performance equivalent to the ideal double layer planar heterostructure (DLPH) detector. Comparable responsivity, low current denisty ‫ܬ‬ ୢୟ୰୩ , and high detectivity ‫ܦ‬ ‫כ‬ values rival those of the DLPH device without requiring p-type doping. The theoretical results suggests that the HgCdTe nBn structure may be a promising solution for achieving a simplified MWIR device structure and addressing problems associated with reducing thermal generation in conventional p-on-n structures and processing technology limitations such as achieving low, controllable in-situ p-type doping with MBE growth techniques. Furthermore, the physical mechanisms for selective carrier conduction in the nBn structure may provide a basis to incorporate into future device structures to suppress intrinsic Auger carrier generation. Likewise, the experimental demonstration of the MWIR HgCdTe nBn devices introduces a promising potential alternative to conventional high performance p-n junction HgCdTe photodiodes. The experiments described in this study illustrate the successful implementation of a HgCdTe barrier-integrated structure. The measured current-voltage characteristics of planar-mesa and mesa HgCdTe nBn devices exhibit barrier-influenced behavior and follow temperature-dependent trends as predicted by numerical simulations. Optical measurements of the planar-mesa MWIR HgCdTe nBn device indicate a bias-dependent spectral response. Further changes to MWIR HgCdTe nBn layer structure has shown an over 10 5 A/cm 2 reduction in J dark as well as a shift to a lower turn-on operation bias. This experimental investigation highlights the potential for pursuing similar and related unipolar, type-I barrier devices for high performance infrared detector applications.

Multiple polycrystalline CdS/CdTe solar cells with efficiencies greater than 15% were produced on buffered, commercially-available Pilkington TEC Glass TM at EPIR Technologies, Inc. (EPIR) and verified by the National Renewable Energy Laboratory (NREL). n-CdS and p-CdTe were grown by chemical bath deposition (CBD) and close space sublimation, respectively. Samples with sputter-deposited CdS were also investigated. Initial results indicate that this is a viable dry-process alternative to CBD for production-scale processing. Published results for polycrystalline CdS/CdTe solar cells with high efficiencies are typically based upon cells utilizing research-grade transparent conducting oxides (TCOs) requiring high-temperature processing inconducive to low-cost manufacturing. EPIR's results for cells on commercial glass were obtained by implementing a high resistivity SnO 2 buffer layer and optimizing the CdS window layer thickness. The high resistivity buffer layer prevents the formation of CdTe-TCO junctions, thereby maintaining a high open circuit voltage and fill factor; while using a thin CdS layer reduces absorption losses and improves the short circuit current density. EPIR's best device demonstrated an NREL-verified efficiency of 15.3%. The mean efficiency of hundreds of cells produced with a buffer layer between December 2010 and June 2011 is 14.4%. Quantum efficiency results are presented to demonstrate EPIR's progress toward NREL's best-published results.

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Hyperspectral infrared imagers are of great interest in applications requiring remote identification of complex chemical agents. The combination of mercury cadmium telluride detectors and Fabry-Perot filters (FPFs) is highly desirable for hyperspectral detection over a broad wavelength range. The geometries of distributed Bragg reflector (DBR)-based tunable FPFs are modeled to achieve a desired spectral resolution and wavelength range. Additionally, acceptable fabrication tolerances are determined by modeling the spectral performance of the FPFs as a function of DBR surface roughness and membrane curvature. These fabrication nonidealities are then mitigated by developing an optimized DBR process flow yielding high-performance FPF cavities suitable for integration with hyperspectral imagers. Downloaded From: http://nanolithography.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms

The combination of HgCdTe detectors and Fabry-Pérot filters (FPFs) is highly desirable for hyperspectral detection in the infrared band over a broad wavelength range. The results of comprehensive modeling of distributedBragg-reflector-based tunable FPFs that can be used with HgCdTe array detectors for hyperspectral imaging modules are presented, focusing on the impact of FPF non-idealities on optical performance. The effects of surface and interface roughness on the spectral resolution and transmissivity of the cavity was explored to determine if certain thin film deposition techniques are suitable to economically fabricate FPFs. The impact of varying field-of-view (FOV) and incident angles are also discussed. Finally, the impact of FPF bowing on spectral resolution is discussed.