Development of Low Stress Ohmic Contacts to HgCdTe
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AbstractThe problem to be solved in the proposed work is that the deposition of the usual In and Au metal contacts on HgCdTe-based IR detectors creates additional stress in the HgCdTe immediately below the contacts, This stress has been observed to getter threading dislocations, which, in turn, creates misfit dislocation segments just below the detector surface and parallel to the surface, in the active area under and close to the contacts. The dangling bonds across these dislocations enhance random generation-recombination processes, thereby reducing quantum efficiencies and detectivities. Because of their location, these misfit dislocations act as especially efficient trapping and recombination centers and strongly degrade detector performance, especially in the long wavelength and very long wavelength ranges. They degrade the zero-bias impedance (R0A) and increase the dark current. The dangling bonds across these dislocations enhance random generation-recombination processes, thereby reducing quantum efficiencies and detectivities. We propose to eliminate or greatly reduce this gettering of threading dislocations and the resultant formation of misfit dislocations by contact deposition on HgCdTe long wavelength infrared (LWIR) detectors.
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