Strain and composition effects on Raman vibrational modes of silicon-germanium-tin ternary alloys

Fournier-Lupien, Jean-Hughes; Mukherjee, Samik; Wirths, Stephan; Pippel, Eckhard; Hayazawa, Norihiko; Mußler, Gregor; Hartmann, Jean‐Michel; Desjardins, P.; Buca, D.; Moutanabbir, Oussama

doi:10.1063/1.4855436

Cited by 71 publications

(78 citation statements)

References 22 publications

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“…shows the Raman spectra obtained with the same acquisition conditions and normalized to the Ge-Ge phonon mode intensity, for three samples, bulk c-Ge (wafer), reference layer of germanium without Sn (#0) and GeSn sample #6 (the one with the highest Sn content). According to the previous studies[11-14, 27, 33-35], for this system it is expected to observe several Raman features, namely: (i) Ge-Ge phonon mode (near 300 cm -1 ), either from the GeSn layers or from the Ge buffer layer or both, (ii) the TO-LO phonon mode of the Si substrate (521 cm -1 ), (iii) a vibration mode due to the Ge-Sn bonds (around 260 cm -1 ), and (iv) possibly a weak band around 185 cm -1 , which has been tentatively attributed to Sn-Sn vibrations by some authors[11], supported mostly by its proximity to the Γ point TO-LO phonon mode in grey tin[46].FromFig. 8it is seen that the reference sample (without tin) exhibits the Ge-Ge phonon mode (the only one seen for the c-Ge) and also the bulk Si-Si phonon mode from the substrate (≈ 520 cm -1 ).…”

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confidence: 86%

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Structural and vibrational properties of SnxGe1-x: Modeling and experiments

Vasin

Oliveira

Cerqueira

et al. 2018

Journal of Applied Physics

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The effects of composition and macroscopic strain on the structural properties and lattice vibrations of SnxGe1-x solid solutions (SSs) are investigated numerically, employing Tersoff empirical inter-atomic potentials, and experimentally. The calculations provide statistical distributions of bond lengths, pair correlation function and vibrational Raman spectra of the SSs. Using this approach, we are able to evaluate the tin-content-dependent shifts due to the local environment (i.e changes in the atomic mass and bond stiffness) and strain effects in the calculated Raman spectra and compare them to experimental data. The relative importance of the composition dependent effects of the local environment and strain for epitaxial layers of GeSn solid solutions is analysed.

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confidence: 86%

“…phonon-related thermal conductivity of SixGe1-x crystals [23]. They are much less expensive in terms of computation time and well suited for modelling effects of strain relaxation in alloys where the end members have different lattice constants [24][25][26], as it is the case of the system under consideration in this work [11,12,27].…”

Section: Introductionmentioning

confidence: 99%

Structural and vibrational properties of SnxGe1-x: Modeling and experiments

Vasin

Oliveira

Cerqueira

et al. 2018

Journal of Applied Physics

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“…The samples investigated in this work were grown using a metal cold-wall reduced pressure chemical vapor deposition (CVD) [10,25,26] [27]. Fig.1(a) shows the STEM images of the layer with highest Sn content Si .…”

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confidence: 99%

Short-range atomic ordering in nonequilibrium silicon-germanium-tin semiconductors

et al. 2017

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The precise knowledge of the atomic order in monocrystalline alloys is fundamental to understand and predict their physical properties. With this perspective, we utilized laser-assisted atom probe tomography to investigate the three-dimensional distribution of atoms in nonequilibrium epitaxial Sn-rich group IV SiGeSn ternary semiconductors. Different atom probe statistical analysis tools including frequency distribution analysis, partial radial distribution functions, and nearest neighbor analysis were employed in order to evaluate and compare the behavior of the three elements to their spatial distributions in an ideal solid solution. This atomistic-level analysis provided clear evidence of an unexpected repulsive interaction between Sn and Si leading to the deviation of Si atoms from the theoretical random distribution. This departure from an ideal solid solution is supported by first principles calculations and attributed to the tendency of the system to reduce its mixing enthalpy throughout the layer-by-layer growth process. 2The assumption that the arrangement of atoms within the crystal lattice is perfectly random is a broadly used approximation to establish the physical properties of semiconductor alloys. This approximation allows one to estimate rather accurately certain thermodynamic as well as material parameters like the excess enthalpy of formation, Vegard-like lattice parameters, and band gaps that are smaller than the composition weighted average (optical bowing). However, it has been proposed that some ternary semiconductors can deviate from this assumed perfect solid solution. Indeed, both calculations and experiments suggested the presence of local atomic order in certain III-V alloys [1][2][3][4][5][6][7][8]. This phenomenon manifests itself when at least one of the elements forming the alloy preferentially occupies or avoids specific lattice sites. This induces short-range order in the lattice with an impact on the basic properties of the alloyed semiconductors [3][4][5][6][7].The recent progress in developing Sn-rich group IV (SiGeSn) ternary semiconductors and their integration in a variety of low dimensional systems and devices have revived the interest in elucidating the atomistic-level properties of monocrystalline alloys [9][10][11][12][13][14][15][16][17][18][19][20]. Interestingly, unlike III-V semiconductors, achieving a direct bandgap in Si GeSn requires a sizable incorporation of Sn 10 . % , which is significantly higher than the equilibrium solubility (<1 at.%). Understanding the atomic structure of these metastable alloys is therefore imperative for implementing predictive models to describe their basic properties. With this perspective, we present a first study of the atomic order in Si Ge Sn alloys (x and y in 0.04 0.19 and 0.02 0.12 range, respectively). We employed Atom Probe Tomography (APT) which allows atomistic level investigations [21][22][23][24] and statistical tools to analyze the three-dimensional (3-D)distributions of the three elements. This analysis unraveled an un...

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“…The calculation of the angular frequency of the phonons involved in the SRS process represents a preliminary step toward the overall model execution. To this purpose, some authors have recently demonstrated that the experimental Raman shift in bulk Ge matches the following relationship with a very good agreement [23]:…”

Section: Numerical Resultsmentioning

confidence: 75%

Investigation of germanium Raman lasers for the mid-infrared

et al. 2015

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In this paper we present a detailed theoretical investigation of integrated racetrack Raman lasers based on the germanium material system operating in the mid-infrared beyond the germanium two-photon absorption cut-off wavelength of 3.17 μm. The effective Raman gain has been estimated in waveguides based on germanium-on-silicon, germanium-on-SOI and germanium-on-Si3N4 technology platforms as a function of their crystallographic orientations. Furthermore, general design guidelines have been determined by means of a comparative analysis of Raman laser performance, i.e. the threshold power, polarization and directionality of the excited Stokes signals as a function of racetrack cavity length and directional-coupler dimensions. Finally, the emitted Raman laser power has been evaluated as a function of overall propagation losses and operative wavelengths up to 3.8 μm, while the time dynamics of Raman lasers has been simulated assuming continuous and pulse waves as input pump signals.

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Strain and composition effects on Raman vibrational modes of silicon-germanium-tin ternary alloys

Cited by 71 publications

References 22 publications

Structural and vibrational properties of SnxGe1-x: Modeling and experiments

Structural and vibrational properties of SnxGe1-x: Modeling and experiments

Short-range atomic ordering in nonequilibrium silicon-germanium-tin semiconductors

Investigation of germanium Raman lasers for the mid-infrared

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