Comparison study of temperature dependent direct/indirect bandgap emissions of Ge 1-x-y Si x Sn y and Ge 1-y Sn y grown on Ge buffered Si

Buguo Wang, T. R. Harris, M. R. Hogsed, Y. K. Yeo, Mee Yi Ryu, John Kouvetakis

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    Temperature-dependent photoluminescence (PL) of two sets of ternary samples with fixed tin concentrations of ~5.2% (Ge 0.924 Si 0.024 Sn 0.052 , and Ge 0.911 Si 0.036 Sn 0.053 ) and ~7.3% (Ge 0.90 0 Si 0.027 Sn 0.073 , and Ge 0.888 Si 0.04 Sn 0.072 ) were measured along with their binary counterparts (Ge 0.948 Sn 0.052 and Ge 0.925 Sn 0.075 ). The variations of direct bandgap emission (E D ) and indirect bandgap emission (E ID ) with temperature were studied for both ternary and binary alloys by means of Gaussian curve fitting, and the results are compared. The bandgap widths of ternaries clearly increase after Si incorporation into the GeSn with similar Sn concentrations. It is found that for the ternaries both E D and E ID peak energies are blue shifted, and the energy separation of E D and E ID peaks becomes larger than that of binaries for similar Sn concentrations. Moreover, both E D and E ID peaks appear at room temperature (RT) in the GeSiSn spectra, but the E D peak position is greater than E ID , indicating these ternaries are indirect bandgap materials. Low temperature PL validates the existence of indirect PL emission in Ge 0.90 Si 0.027 Sn 0.073 and direct gap behavior in Ge 0.925 Sn 0.075 , indicating GeSn becomes a direct bandgap material at lower Sn concentration than GeSiSn. The PL intensities of these ternaries are generally weaker and the spectra become more complicated than those of binaries, probably due to increased strain and defects in the ternaries. Finally, it is found that the effect of large differences in strain of ternary samples on PL peak positions can be greater than that of small Si composition differences in ternaries. A large compressive strain in ternaries can also make splitting of the E D into E D,HH (conduction band minimum-Γ valley to heavy hole maximum) and E D,LH (conduction band minimum-Γ valley to light hole maximum) transitions more observable in the PL spectra.

    Original languageEnglish (US)
    Pages (from-to)63-71
    Number of pages9
    JournalThin Solid Films
    Volume673
    DOIs
    StatePublished - Mar 1 2019

    Fingerprint

    Photoluminescence
    Energy gap
    photoluminescence
    Conduction bands
    Temperature
    temperature
    valleys
    conduction bands
    Ternary alloys
    Tin
    ternary alloys
    Binary alloys
    curve fitting
    Curve fitting
    binary alloys
    low concentrations
    tin
    Defects
    energy
    defects

    Keywords

    • Direct/indirect bandgap emissions
    • Germanium silicon tin
    • Germanium tin
    • Photoluminescence
    • Strain
    • Valence band splitting

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Surfaces and Interfaces
    • Surfaces, Coatings and Films
    • Metals and Alloys
    • Materials Chemistry

    Cite this

    Comparison study of temperature dependent direct/indirect bandgap emissions of Ge 1-x-y Si x Sn y and Ge 1-y Sn y grown on Ge buffered Si . / Wang, Buguo; Harris, T. R.; Hogsed, M. R.; Yeo, Y. K.; Ryu, Mee Yi; Kouvetakis, John.

    In: Thin Solid Films, Vol. 673, 01.03.2019, p. 63-71.

    Research output: Contribution to journalArticle

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    abstract = "Temperature-dependent photoluminescence (PL) of two sets of ternary samples with fixed tin concentrations of ~5.2{\%} (Ge 0.924 Si 0.024 Sn 0.052 , and Ge 0.911 Si 0.036 Sn 0.053 ) and ~7.3{\%} (Ge 0.90 0 Si 0.027 Sn 0.073 , and Ge 0.888 Si 0.04 Sn 0.072 ) were measured along with their binary counterparts (Ge 0.948 Sn 0.052 and Ge 0.925 Sn 0.075 ). The variations of direct bandgap emission (E D ) and indirect bandgap emission (E ID ) with temperature were studied for both ternary and binary alloys by means of Gaussian curve fitting, and the results are compared. The bandgap widths of ternaries clearly increase after Si incorporation into the GeSn with similar Sn concentrations. It is found that for the ternaries both E D and E ID peak energies are blue shifted, and the energy separation of E D and E ID peaks becomes larger than that of binaries for similar Sn concentrations. Moreover, both E D and E ID peaks appear at room temperature (RT) in the GeSiSn spectra, but the E D peak position is greater than E ID , indicating these ternaries are indirect bandgap materials. Low temperature PL validates the existence of indirect PL emission in Ge 0.90 Si 0.027 Sn 0.073 and direct gap behavior in Ge 0.925 Sn 0.075 , indicating GeSn becomes a direct bandgap material at lower Sn concentration than GeSiSn. The PL intensities of these ternaries are generally weaker and the spectra become more complicated than those of binaries, probably due to increased strain and defects in the ternaries. Finally, it is found that the effect of large differences in strain of ternary samples on PL peak positions can be greater than that of small Si composition differences in ternaries. A large compressive strain in ternaries can also make splitting of the E D into E D,HH (conduction band minimum-Γ valley to heavy hole maximum) and E D,LH (conduction band minimum-Γ valley to light hole maximum) transitions more observable in the PL spectra.",
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    AU - Wang, Buguo

    AU - Harris, T. R.

    AU - Hogsed, M. R.

    AU - Yeo, Y. K.

    AU - Ryu, Mee Yi

    AU - Kouvetakis, John

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    N2 - Temperature-dependent photoluminescence (PL) of two sets of ternary samples with fixed tin concentrations of ~5.2% (Ge 0.924 Si 0.024 Sn 0.052 , and Ge 0.911 Si 0.036 Sn 0.053 ) and ~7.3% (Ge 0.90 0 Si 0.027 Sn 0.073 , and Ge 0.888 Si 0.04 Sn 0.072 ) were measured along with their binary counterparts (Ge 0.948 Sn 0.052 and Ge 0.925 Sn 0.075 ). The variations of direct bandgap emission (E D ) and indirect bandgap emission (E ID ) with temperature were studied for both ternary and binary alloys by means of Gaussian curve fitting, and the results are compared. The bandgap widths of ternaries clearly increase after Si incorporation into the GeSn with similar Sn concentrations. It is found that for the ternaries both E D and E ID peak energies are blue shifted, and the energy separation of E D and E ID peaks becomes larger than that of binaries for similar Sn concentrations. Moreover, both E D and E ID peaks appear at room temperature (RT) in the GeSiSn spectra, but the E D peak position is greater than E ID , indicating these ternaries are indirect bandgap materials. Low temperature PL validates the existence of indirect PL emission in Ge 0.90 Si 0.027 Sn 0.073 and direct gap behavior in Ge 0.925 Sn 0.075 , indicating GeSn becomes a direct bandgap material at lower Sn concentration than GeSiSn. The PL intensities of these ternaries are generally weaker and the spectra become more complicated than those of binaries, probably due to increased strain and defects in the ternaries. Finally, it is found that the effect of large differences in strain of ternary samples on PL peak positions can be greater than that of small Si composition differences in ternaries. A large compressive strain in ternaries can also make splitting of the E D into E D,HH (conduction band minimum-Γ valley to heavy hole maximum) and E D,LH (conduction band minimum-Γ valley to light hole maximum) transitions more observable in the PL spectra.

    AB - Temperature-dependent photoluminescence (PL) of two sets of ternary samples with fixed tin concentrations of ~5.2% (Ge 0.924 Si 0.024 Sn 0.052 , and Ge 0.911 Si 0.036 Sn 0.053 ) and ~7.3% (Ge 0.90 0 Si 0.027 Sn 0.073 , and Ge 0.888 Si 0.04 Sn 0.072 ) were measured along with their binary counterparts (Ge 0.948 Sn 0.052 and Ge 0.925 Sn 0.075 ). The variations of direct bandgap emission (E D ) and indirect bandgap emission (E ID ) with temperature were studied for both ternary and binary alloys by means of Gaussian curve fitting, and the results are compared. The bandgap widths of ternaries clearly increase after Si incorporation into the GeSn with similar Sn concentrations. It is found that for the ternaries both E D and E ID peak energies are blue shifted, and the energy separation of E D and E ID peaks becomes larger than that of binaries for similar Sn concentrations. Moreover, both E D and E ID peaks appear at room temperature (RT) in the GeSiSn spectra, but the E D peak position is greater than E ID , indicating these ternaries are indirect bandgap materials. Low temperature PL validates the existence of indirect PL emission in Ge 0.90 Si 0.027 Sn 0.073 and direct gap behavior in Ge 0.925 Sn 0.075 , indicating GeSn becomes a direct bandgap material at lower Sn concentration than GeSiSn. The PL intensities of these ternaries are generally weaker and the spectra become more complicated than those of binaries, probably due to increased strain and defects in the ternaries. Finally, it is found that the effect of large differences in strain of ternary samples on PL peak positions can be greater than that of small Si composition differences in ternaries. A large compressive strain in ternaries can also make splitting of the E D into E D,HH (conduction band minimum-Γ valley to heavy hole maximum) and E D,LH (conduction band minimum-Γ valley to light hole maximum) transitions more observable in the PL spectra.

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    KW - Germanium silicon tin

    KW - Germanium tin

    KW - Photoluminescence

    KW - Strain

    KW - Valence band splitting

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