Electrical and optical properties improvement of GeSn layers formed at high temperature under well-controlled Sn migration

Taoka, Noriyuki; Capellini, Giovanni; Schlykow, Viktoria; Montanari, Michele; Zaumseil, P.; Nakatsuka, Osamu; Zaima, Shigeaki; Schroeder, Thomas

doi:10.1016/j.mssp.2016.09.040

Cited by 17 publications

(15 citation statements)

References 26 publications

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“…by rapid thermal annealing, and the films are usually highly strained. 38,39,40 This paper provides insight in the formation mechanism of anisotropic Ge 1−x Sn x structures at temperatures as low as 140 °C leading to a Sn content of 28 %, while the formation of -Sn for this low temperature process is elaborated. Two distinct compositions have been reliably synthesised with two different temperature profiles and pretreatment processes leading to Sn contents of ~17 % and ~28 % and without additional nucleation of branches or substructures.…”

Section: Introductionmentioning

confidence: 97%

Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability

et al. 2017

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Ge 1−x Sn x nanorods (NRs) with a nominal Sn content of 28% have been prepared by a modified microwavebased approach at very low temperature (140 °C) with Sn as growth promoter. The observation of a Sn-enriched region at the nucleation site of NRs and the presence of the low temperature -Sn phase even at elevated temperatures support a template-supported formation mechanism. The behaviour of two distinct Ge 1−x Sn x compositions with high Sn content of 17% and 28% upon thermal treatment has been studied and reveal segregation events occurring at elevated temperatures, but also demonstrate the temperature window of thermal stability. In situ transmission electron microscopy investigations revealed a diffusion of metallic Sn clusters through the Ge 1−x Sn x NRs associated with temperatures where the material composition changes drastically. These results are important for the explanation of distinct composition changes in Ge 1−x Sn x and the observation of solid diffusion combined with dissolution and redeposition of Ge 1−y Sn y (x>y) exhibiting a reduced Sn content. Absence of metallic Sn results in increased temperature stability by ~70 °C for Ge 0.72 Sn 28 NRs and ~60 °C for Ge 0.83 Sn 17 nanowires (NWs). In addition, a composition-dependent direct bandgap of the Ge 1−x Sn x NRs and NWs with different composition is illustrated using Tauc plots. ASSOCIATED CONTENT Supporting Information. Additional SEM, TEM, EDX and XRD data are provided. Moreover, a video for the phase separation in the TEM is supplied. This material is available free of charge via the Internet at http://pubs.acs.org.

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Section: Introductionmentioning

confidence: 97%

Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability

et al. 2017

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“…Recently, there are also some reports on the synthesis of GeSn [21][22][23] and SiGe [20,24,25]. However, there is no experimental report on the synthesis of SnC.…”

Section: Introductionmentioning

confidence: 99%

First principle and tight-binding study of strained SnC

Moğulkoç

Modarresi

Moğulkoç

et al. 2017

Journal of Physics and Chemistry of Solids

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We study the electronic and optical properties of strained single-layer SnC in the density functional theory (DFT) and tightbinding models. We extract the hopping parameters tight-binding Hamiltonian for monolayer SnC by considering the DFT results as a reference point. We also examine the phonon spectra in the scheme of DFT, and analyze the bonding character by using Mulliken bond population. Moreover, we show that the band gap modulation and transition from indirect to direct band gap in the compressive strained SnC. The applied tensile strain reduces the band gap and eventually the semiconductor to semimetal transition occurs for 7.5% of tensile strain. In the framework of tight-binding model, the effect of spin-orbit coupling on energy spectrum are also discussed. We indicate that while tensile strain closes the band gap, spin-orbit gap is still present which is order of ∼ 40 meV at the Γ point. The substrate effect is modeled through a staggered sub-lattice potential in the tight-binding approximation. The optical properties of pristine and strained SnC are also examined in the DFT scheme. We present the modulation of real and imaginary parts of dielectric function under applied strain.

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“…18,22 Therefore, to obtain high quality and direct bandgap GeSn alloy, the dilemma between the Sn segregation at a high growth temperature and the high defect density introduced at a low growth temperature must be overcome. 23 Thermal annealing leads to decrease in defect density and improves optical quality of the GeSn alloy. 24 At the same time, thermal annealing could also increase the portion of substitutional Sn atoms to reduce the difficulty of realizing direct bandgap luminescence.…”

Section: Introductionmentioning

confidence: 99%

“…24,25 Proper annealing temperature has been found to be 500 • C by measuring the root mean square (RMS) roughness and average of aligned yield (from RBS) 26 or 550 • C by using photoluminescence (PL). 23 For a partially relaxed GeSn alloy, the bandgap transition occurs when the Sn concentration is 6∼11%. [1][2][3]27,28 When the GeSn alloy is fully strained on a Ge substrate, the bandgap transformation from the indirect bandgap to the direct bandgap even occurs at 12%.…”

Section: Introductionmentioning

confidence: 99%

Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy

Zhang

Song

et al. 2017

AIP Advances

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GeSn alloy with 7.68% Sn concentration grown by molecular beam epitaxy has been rapidly annealed at different temperatures from 300°C to 800°C. Surface morphology and roughness annealed below or equal to 500°C for 1 min have no obvious changes, while the strain relaxation rate increasing. When the annealing temperature is above or equal to 600°C, significant changes occur in surface morphology and roughness, and Sn precipitation is observed at 700°C. The structural properties are analyzed by reciprocal space mapping in the symmetric (004) and asymmetric (224) planes by high resolution X-ray diffraction. The lateral correlation length and the mosaic spread are extracted for the epi-layer peaks in the asymmetric (224) diffraction. The most suitable annealing temperature to improve both the GeSn lattice quality and relaxation rate is about 500°C.

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Electrical and optical properties improvement of GeSn layers formed at high temperature under well-controlled Sn migration

Cited by 17 publications

References 26 publications

Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability

Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability

First principle and tight-binding study of strained SnC

Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy

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Electrical and optical properties improvement of GeSn layers formed at high temperature under well-controlled Sn migration

Cited by 17 publications

References 26 publications

Pushing the Composition Limit of Anisotropic Ge1–xSnx Nanostructures and Determination of Their Thermal Stability

Pushing the Composition Limit of Anisotropic Ge1–xSnx Nanostructures and Determination of Their Thermal Stability

First principle and tight-binding study of strained SnC

Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy

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Product

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Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability

Pushing the Composition Limit of Anisotropic Ge_1–xSn_x Nanostructures and Determination of Their Thermal Stability