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Recent prototypes of the individual identification friend or foe (IIFF) patch use a light-emitting electrochemical cell (LEC) as the emitter. This research characterizes the transient behavior of LECs by measuring transient capacitance. The transient capacitance data are important to improve understanding of the underlying physics describing the operation of the LEC. The research goal was to make the first transient measurements of an LEC's capacitance as a function of temperature and bias, while simultaneously measuring the transient light output and current, to monitor in-situ junction formation inside an LEC. Capacitance changes varying from 5-30 nF are measured, depending on applied voltage and device temperature. Strong temperature dependence of the rate of change of capacitance suggests Arrhenius-type behavior associated with ion motion with an activation energy of 1.27 eV. The initial rate of change of capacitance is faster than the rate of change of light and current, suggesting that modification of the field near the contacts plays a key role in controlling free carrier injection. Initially capacitance increases monotonically upon application of bias, however, at longer times decreasing and even oscillating capacitance has been observed. This behavior provides new information on the dynamics of ion motion and carrier injection in LECs. Approved for public release; distribution is unlimited.

The objective of this research was to demonstrate the extension of the current design of the Individual Identification Friend or Foe (IIFF) patch, to provide a response in the shortwave infrared (SWIR) region of the electromagnetic spectrum. The purpose of the IIFF patch is to mitigate fratricide during ground engagements, by emitting a near infrared (NIR) signal when the wearer is illuminated by a targeting laser attached to the shooter's weapon. Due to the proliferation of NIR Night Vision Devices (NVDs), it is desirable to produce a version of the patch that emits in the SWIR spectrum, making its response visible to operators with next-generation NVDs, while being invisible to conventional NVDs. This further enhances the "covert" nature of the IIFF patch. To produce SWIR output, a visible-light emitter is used in conjunction with a downconverting phosphor filter. This thesis develops and evaluates candidates for visible-light emitters and downconverting phosphor filters in order to determine the most suitable candidate for use in the IIFF patch. Three potential candidate materials, based on neodymium and ytterbium phosphors, were evaluated using photoluminescence excitation spectroscopy. A quantitative comparison of the combined efficiency was performed to select an initial optimized combination. SWIR emission was observed through an InGaAs imaging array. http://archive.org/details/visibletoswirdow109454715 US Navy (USN) author. Approved for public release; distribution is unlimited.

A new technique for imaging the 2D transport of free charge in semiconductor structures is used to directly map electric field distributions in operating devices. Direct transport imaging is demonstrated in a scanning electron microscope, using an optical microscope and a high sensitivity charge coupled device. Transport behavior under the combined influence of both diffusion and drift is predicted by modeling the drift and diffusion in 2D following generation at a point source. This is the first demonstration of a technique that allows the mapping of the electric field by determining not only the direction but especially the magnitude of the electric field with high resolution. The measured results show excellent agreement with theoretical predictions simulated with COMSOL software. The transport imaging technique also allows measurement of the contact resistance in a new way that is nondestructive and based on a two-point contact only. The technique illustrates the device's characteristics by determining the exact activation point of the diode and the deviations from an ideal I-V behavior. The method is extremely useful since the complexity and miniaturization of current devices do not allow for multiple wiring that standard four point measurement demands. Finally, a suggestion for further research of the effects of electromigration by using the direct transport imaging technique is offered. The latter is a subject of high importance in electronic device reliability. http://archive.org/details/directelectricfi109452398 Approved for public release; distribution is unlimited.

An optical, contact-free method for measuring minority carrier diffusion lengths is developed and demonstrated for a range of semiconductor materials used in high efficiency triple junction solar cells. This method uses a Scanning Electron Microscope (SEM) coupled with an optical microscope. The diffusion lengths, combined with minority carrier lifetime measured via time-resolved photoluminescence, allow for the computation of minority charge carrier mobility. The technique uses images to extract diffusion length measurements from GaAs, InGaAs, and InGaP heterostructures at different SEM beam energies and probe currents. Excellent correlation between measurements shows the reproducibility of this technique. Diffusion lengths from 2-63 microns have been measured in a variety of GaAs, InGaAs, and InGaP samples. Effects of alloy ordering, doping, and lattice matching have been investigated. Several areas for further research are offered, including detailed radiationdamage mapping of solar cell layers. Further anisotropic studies of the solar cell layers are suggested to investigate the directional dependence of diffusion length within the InGaP heterostructures. Finally, new and emerging solar cell materials would benefit from this technique, allowing for the complete characterization of minority charge transport properties before growing an entire solar cell. http://archive.org/details/directimagingofm109452472 Approved for public release; distribution is unlimited.

The minority carrier diffusion length is a critical parameter in the development of next generation Heterostructure Bipolar Transistors (HBT) and highly efficient solar cells. A novel technique has been developed utilizing direct imaging of electron/hole recombination via an optical microscope and a high sensitivity charge coupled device coupled to a scanning electron microscope to capture spatial information about the transport behavior (diffusion lengths/drift lengths) in luminescent solid state materials. In this work, a numerical model was developed to do a multi-parameter least squares analysis of transport images. Results were applied to the study of transport in materials at the forefront of device technology that are affected by quantum scattering effects, where few reliable experimental measurements exist. The technique allows for easy localization of the measurement site, broad application to a range of materials and potential industrial automation to aid electronics for terahertz devices. http://archive.org/details/transportimaging109451851 Outstanding Thesis Approved for public release; distribution is unlimited.

A quantitative method for extracting minority carrier diffusion and drift lengths is developed and demonstrated in a heavily-doped semiconductor heterostructure. This method advances the high resolution transport imaging technique, yielding key material parameters with a single, non-destructive measurement. This is the first demonstration of an SEM-based, contact-free, non-destructive technique for high-resolution minority carrier lifetime measurement. The measured values are in excellent agreement with theoretical calculations. The imaging transport technique is also employed to image the nature of the generation region as a function of beam energy, probe current and sample atomic number. These types of images should be useful to allow for experimental verification of resolution limits in CL and EBIC associated with interaction volume effects in bulk materials and can be obtained without additional sample preparation. Finally, several suggestions for further research are offered, including mapping of radiation damage in solar cells, near-contact E field mapping and studies of low-dimensional structures such as superlattices and quantum wires. These nanoscale structures are poised to usher-in the next revolution in solid-state electronic devices. http://archive.org/details/directimagingofm109451952 Approved for public release; distribution is unlimited.

Silicon Blocked Impurity Band (BIB) detectors are state-of-the-art devices to detect light in the near to mid infrared range (5-40 æm). Numerical modeling of BIB detectors is performed using a four-region finite difference approach to study the role of space charge in C-V (capacitance-voltage) profiling of minority carrier doping and the role of blocking layer thickness and minority doping concentration in alternate bias operation. Compensation in the blocking layer is found to play a critical role in determining the net voltage drop in this part of the device under alternate polarity bias. The effect of space charge at the blocking layer/active layer interface on the measured low temperature C-V distribution is modeled as a function of the doping interface between the two layers. The magnitude of the space charge can cause large deviations in the measurement of minority doping concentration from the idealized case which assumes a space-charge free blocking layer and interface. Accurately determining these minority doping concentrations is a crucial step toward solving material growth challenges in proposed far infrared Ge and GaAs devices. http://archive.org/details/modelinglowtempe109452102 Approved for public release; distribution is unlimited.