A III-nitride Layered Barrier Structure for Hyperspectral Imaging Applications
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1167-O06-03
A III-Nitride Layered Barrier Structure for Hyperspectral Imaging Applications L. D. Bell1, N. Tripathi2, J. R. Grandusky2, V. Jindal2, and F. Shahedipour-Sandvik2 1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 2 College of Nanoscale Science and Engineering, University at Albany, Albany, NY 12203 ABSTRACT We report on a novel photodetector structure based on III-nitride materials. A layered configuration is used to create a barrier with voltage-tunable height. The barrier is used as a filter for photoexcited holes and electrons, and could form the basis for a dynamically tunable pixel in a hyperspectral imaging array. This would eliminate the need for external gratings and filters used in conventional hyperspectral instruments. In addition, the tunability of pixels allows a decrease of the array dimension by one. The III-nitride materials family is a good candidate for this device, combining large band offsets with the ability for epitaxial growth. We have demonstrated the feasibility of using III-nitride materials to fabricate layered tunnel barriers and have demonstrated tunability of photodetection using these structures. External quantum efficiencies of > 12% have been achieved with prototype devices. INTRODUCTION Improvement in III-nitride growth methods and material quality has led to many applications of this material system for optical and electronic devices, including light emitting diodes[1,2,3,4] (LEDs), laser diodes[5] (LDs), visible and ultraviolet detectors[6], and high electron mobility transistors[7]. A proposed new application of this material system is for a layered barrier heterostructure to be used as the critical element in a tunable hyperspectral detector. Hyperspectral imaging, or imaging spectrometry, has important applications to the remote investigation of both the Earth's surface and of the outer planets and moons [8,9] via chemical composition mapping and analysis. The characterization of surfaces and atmospheres requires chemical composition mapping and analysis, and hyperspectral imaging provides critical information on the surface composition, atmosphere, and temperature. Human-made objects can also be identified and classified. Since the technique provides chemical information on vegetation as well as inorganic materials, it is also valuable for resource identification. Deployment can be airborne or orbital. Conventional hyperspectral imagers use an external grating to disperse the incoming light along one spatial dimension of a detector array. Different configurations for the imager are possible. A 1D detector array can be used to capture spectral information for a single spatial pixel, in conjunction with a mechanical raster to assemble a spatial image line. Vehicle motion along the flight direction provides the raster in the other spatial dimension. Thus this type of "whiskbroom" operation requires only a linear array. Alternatively, in the “pushbroom” configuration, a 2D array can be used to record spectral information and one spat
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