High Purity GaAs Far IR Photoconductor With Enhanced Quantum Efficieny
National Aeronautics and Space Administration
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P.O. Box 60658, Palo Alto, CA, 94306-2306
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AbstractThis proposal introduces an innovative concept aimed to significantly enhance the quantum efficiency of a far-infrared GaAs photoconductor and achieve sensitivity levels of 10E-18 W/SQRT(Hz) or better. We propose to employ a microwave source to assist the photoionization process by pumping the infrared-generated electrons from the excited states to the continuum. Since the microwave photons are low in energy, they are not available to directly ionize the ground state of the shallow donors. Therefore, the microwave pumping process is not expected to generate additional leakage current and the associated noise. This will allow us to cool the detector as low as necessary to reduce the thermal leakage current and improve the detector's noise performance. GaAs covers the 100-310?m spectrum where no other photodetector operates, it can be fabricated in large arrays, and is compatible with the established silicon readout technology. The proposed concept can be applied in a broader scope to other photodetectors, such as Ge:Ga, to exploit their excited state photoconductivity and extend their long wavelength response. This effort fits well within the scope of the SBIR Subtopic S2.01 and will be a benefit to many large and small NASA projects such as SOFIA and SAFIR.
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