Abstract
We report on the development of Germanium Blocked Impurity Band (BIB) photoconductors for long wavelength infrared detection in the 100 to 250.fum region. Liquid Phase Epitaxy (LPE) was used to grow the high purity blocking layer, and in some cases, the heavily doped infrared absorbing layer that comprise theses detectors. To achieve the stringent demands on purity and crystalline perfection we have developed a high purity LPE process which can be used for the growth of high purity as well as purely doped Ge epilayers. The low melting point, high purity metal, Pb, was used as a solvent. Pb has a negligible solubility <1017 cm-3 in Ge at 650°C and is isoelectronic with Ge. We have identified the residual impurities Bi, P, and Sb in the Ge epilayers and have determined that the Pb solvent is the source. Experiments are in progress to purify the Pb. The first tests of BIB structures with the purely doped absorbing layer grown on high purity substrates look very promising. The detectors exhibit extended wavelength cutoff when compared to standard Ge:Ga photoconductors (155 fum vs. 120 fum) and show the expected asymmetric current-voltage dependencies. We are currently optimizing doping and layer thickness to achieve the optimum responsivity, Noise Equivalent Power (NEP), and dark current in our devices.
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Acknowledgement
This work was supported by National Aeronautics and Space Administration under contracts W17605 and A59513C through interagency agreement with U.S. Department of Energy under contract DE-AC03-76SF00098. C.S. olsen acknowledges fellowship support from Applied Materials Inc.
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Olsen, C.S., Beeman, J.W., Hansen, W.L. et al. Germanium Far Infrared Blocked Impurity Band Detectors. MRS Online Proceedings Library 484, 215–220 (1997). https://doi.org/10.1557/PROC-484-215
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DOI: https://doi.org/10.1557/PROC-484-215