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Direct band gap luminescence from Ge on Si pin diodes

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Abstract

Germanium (Ge) pin photodiodes show clear direct band gap emission at room temperature, as grown on bulk silicon in both photoluminescence (PL) and electroluminescence (EL). PL stems from the top contact layer with highly doped Ge because of strong absorption of visible laser light excitation (532 nm). EL stems from the recombination of injected carriers in the undoped intrinsic layer. The difference in peak positions for PL (0.73 eV) and EL (0.80 eV) is explained by band gap narrowing from high doping in n+-top layer. A superlinear increase of EL with current density is explained by a rising ratio of direct/indirect electron densities when quasi Fermi energy level rises into the conduction band. An analytical model for the direct/indirect electron density ratio is given using simplifying assumptions.

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Authors and Affiliations

  1. Institut für Halbleitertechnik (IHT), University of Stuttgart, Stuttgart, 70569, Germany

    E. Kasper, M. Oehme & J. Werner

  2. Joint Lab IHP/BTU Cottbus, Cottbus, 03013, Germany

    T. Aguirov & M. Kittler

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  1. E. Kasper
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  2. M. Oehme
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  3. J. Werner
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  4. T. Aguirov
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  5. M. Kittler
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Correspondence to E. Kasper.

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Kasper, E., Oehme, M., Werner, J. et al. Direct band gap luminescence from Ge on Si pin diodes. Front. Optoelectron. 5, 256–260 (2012). https://doi.org/10.1007/s12200-012-0235-4

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  • DOI: https://doi.org/10.1007/s12200-012-0235-4

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