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The project goal was to design and test a monolithic integrated device for radiation sensing, using optically stimulated luminescence (OSL) from Al2O3:C. The device would consist of GaN/InGaN-based components epitaxially grown on each side of a A12O3:C substrate. Radiation energy stored in the substrate would be stimulated by visible emission from a GaN light-emitting diode (LED) grown on one side of the device, and the OSL emission from the substrate (in the blue region of the spectrum) would be detected by the InGaN pi-n diode grown on the other side of the substrate. The primary application of the device would be in space radiation environments. Thus, two major research thrusts were launched during this project. Firstly, research at Oklahoma State University (Dr. Stephen W.S. McKeever and Dr. E.G. Yukihara) concentrated on characterization of the OSL properties of Al2O3:C in radiation fields typical of those experienced in low-Earth orbit. Secondly, research at the University of Washington (Co-Is, Dr. T.G. Stoebe and Dr. T. Chen) focused of device development and GaN/InGaN epitaxial growth. While progress in each line of research has been substantial, the ultimate goal (that of producing a working prototype device) has not yet been reached. We detail the research progress and identify outstanding issues in this paper.

We describe progress in the development of a close-packed array of bolometers intended for use in photometric applications at millimeter wavelengths from ground- based telescopes. Each bolometer in the may uses a proximity-effect Transition Edge Sensor (TES) sensing element and each will have integrated Normal-Insulator-Superconductor (NIS) refrigerators to cool the bolometer below the ambient bath temperature. The NIS refrigerators and acoustic-phonon-mode-isolated bolometers are fabricated on silicon. The radiation-absorbing element is mechanically suspended by four legs, whose dimensions are used to control and optimize the thermal conductance of the bolometer. Using the technology developed at NIST, we fabricate NIS refrigerators at the base of each of the suspension legs. The NIS refrigerators remove hot electrons by quantum-mechanical tunneling and are expected to cool the biased (approx.10 pW) bolometers to <170 mK while the bolometers are inside a pumped 3He-cooled cryostat operating at approx.280 mK. This significantly lower temperature at the bolometer allows the detectors to approach background-limited performance despite the simple cryogenic system.

The SPEED camera is being developed to study the spectral energy distributions of high redshift galaxies using the Heinrich Hertz Telescope (HHT) in Arizona. SPEED requires a small cryogenic detector array of 2x2 pixels with each pixel having four frequency bands in the 150-350 GHz range. Here we describe the development of the detector array of these high efficiency FSBs. The FSB design provides the multi-pixel multi-spectral band capability required for SPEED in a compact stackable array. The SPEED bolometers will use proximity effect superconducting transition edge sensors as their temperature-sensing element allowing for higher levels of multiplexing in future applications.