We address nonradiative recombination pathways by leveraging surface passivation and dislocation management in μm-scale arrays of Ge crystals grown on deeply patterned Si substrates. The time decay photoluminescence (PL) at cryogenic temperatures discloses carrier lifetimes approaching 45 ns in band-gap engineered Ge micro-crystals. This investigation provides compelling information about the competitive interplay between the radiative band-edge transitions and the trapping of carriers by dislocations and free surfaces. Furthermore, an in-depth analysis of the temperature dependence of the PL, combined with capacitance data and finite difference time domain modeling, demonstrates the effectiveness of GeO2 in passivating the surface of Ge and thus in enhancing the room temperature PL emission.
Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates
Fabio Pezzoli, Anna Giorgioni, Kevin Gallacher, Fabio Isa, Paolo Biagioni, Ross W. Millar, Eleonora Gatti, Emanuele Grilli, Emiliano Bonera, Giovanni Isella, Douglas J. Paul, Leo Miglio; Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates. Appl. Phys. Lett. 27 June 2016; 108 (26): 262103. https://doi.org/10.1063/1.4955020
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