Investigation of Sn surface segregation during GeSn epitaxial growth by Auger electron spectroscopy and energy dispersive x-ray spectroscopy

Tsukamoto, Takahiro; Hirose, Nobuyoshi; Kasamatsu, Akifumi; Mimura, Takashi; Matsui, Toshiaki; Suda, Yoshiyuki

doi:10.1063/1.4907863

Cited by 48 publications

(30 citation statements)

References 22 publications

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“…5,6 This is partially attributed to the large difference (~14.7%) in covalent radius between Ge (1.225Å) and Sn (1.405Å), which also causes a large compressive strain in GeSn when grown on Ge or Si. 7,8 The growth of supersaturated GeSn incorporating more than 1at.% of Sn is achieved using far-from-equilibrium growth conditions, [9][10][11][12] which prevent the formation of a biphasic mixture of Ge-rich and Sn-rich compounds in the early growth stage. 13,14 Yet, as the layers grow thicker, the alloy can undergo phase separation, leading to the nucleation of surface Sn droplets and material degradation.…”

Section: Introductionmentioning

confidence: 99%

Dislocation Pipe Diffusion and Solute Segregation during the Growth of Metastable GeSn

Nicolas

Assali

Mukherjee

et al. 2020

Crystal Growth & Design

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Controlling the growth kinetics from the vapor phase has been a powerful paradigm enabling a variety of metastable epitaxial semiconductors such as Sn-containing group IV semiconductors (Si)GeSn. In addition to its importance for emerging photonic and optoelectronic applications, this class of materials is also a rich platform to highlight the interplay between kinetics and thermodynamic driving forces during growth of strained, nonequilibrium alloys. Indeed, these alloys are inherently strained and supersaturated in Sn and thus can suffer instabilities that are still to be fully elucidated. In this vein, in this work the atomic-scale microstructure of Ge0.82Sn0.18 is investigated at the onset of phase separation as the epitaxial growth aborts. In addition to the expected accumulation of Sn on the surface leading to Sn-rich droplets and sub-surface regions with the anticipated equilibrium Sn composition of 1.0at.%, the diffusion of Sn atoms also yields conspicuous Sn-decorated filaments with nonuniform Sn content in the range of ~1 to 11at.% .The latter are attributed to the formation and propagation of dislocations, facilitating the Sn transport toward the surface through pipe diffusion. Furthermore, the interface between the Sn droplet and GeSn shows a distinct, defective layer with Sn content of ~22at.%. This layer is likely formed by the expelled excess equilibrium Ge as the Sn solidifies, and its content seems to be a consequence of strain minimization between tetragonal Sn-rich and cubic Ge-rich equilibrium phases. The elucidation of these phenomena is crucial to understand the stability of GeSn semiconductors and control their epitaxial growth at a uniform composition.

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Section: Introductionmentioning

confidence: 99%

Dislocation Pipe Diffusion and Solute Segregation during the Growth of Metastable GeSn

Nicolas

Assali

Mukherjee

et al. 2020

Crystal Growth & Design

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“…From material growth perspective, the epitaxy of relaxed high Sn composition GeSn with high material quality is challenging due to the following factors: (i) Low (<1%) equilibrium solid solubility of α-Sn in Ge 8 : Sn atoms tend to segregate during the epitaxy growth and form β-Sn clusters 9 , 10 ; (ii) Small temperature window for GeSn epitaxy growth: Low temperature is required for high Sn incorporation to suppress Sn precipitation. However, low temperature growth easily leads to epitaxial breakdown for thick film due to the severe surface roughening 11 ; (iii) Large lattice mismatch (~15%) between Ge and α-Sn, making relaxed GeSn epitaxy on Ge difficult.…”

Section: Introductionmentioning

confidence: 99%

Investigation of GeSn Strain Relaxation and Spontaneous Composition Gradient for Low-Defect and High-Sn Alloy Growth

Dou

Benamara

Mosleh

et al. 2018

Sci Rep

114

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Recent development of group-IV alloy GeSn indicates its bright future for the application of mid-infrared Si photonics. Relaxed GeSn with high material quality and high Sn composition is highly desirable to cover mid-infrared wavelength. However, its crystal growth remains a great challenge. In this work, a systematic study of GeSn strain relaxation mechanism and its effects on Sn incorporation during the material growth via chemical vapor deposition was conducted. It was discovered that Sn incorporation into Ge lattice sites is limited by high compressive strain rather than historically acknowledged chemical reaction dynamics, which was also confirmed by Gibbs free energy calculation. In-depth material characterizations revealed that: (i) the generation of dislocations at Ge/GeSn interface eases the compressive strain, which offers a favorably increased Sn incorporation; (ii) the formation of dislocation loop near Ge/GeSn interface effectively localizes defects, leading to the subsequent low-defect grown GeSn. Following the discovered growth mechanism, a world-record Sn content of 22.3% was achieved. The experiment result shows that even higher Sn content could be obtained if further continuous growth with the same recipe is conducted. This report offers an essential guidance for the growth of high quality high Sn composition GeSn for future GeSn based optoelectronics.

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“…The change of the superstructure takes place in the region between the first and second extremum, which reduces the stress accumulated in the film and critical thickness of the 2D-3D transition increases. Sn collects on the surface above 325°C due to the segregation [21] and we observe the 2D-3D transition for the layer having the composition close to a double compound with a reduced concentration of Sn at 450°C. The segregation of Sn at the surface of the film depends on the growth temperature, the Sn content and also misfit of lattice parameters of GeSiSn and Si.…”

Section: Resultsmentioning

confidence: 68%

PSEUDOMORPHIC GeSiSn LAYERS IN STRAINED HETEROSTRUCTURES

Никифоров

Тимофеев

Yakimov

et al. 2018

УФЖ

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The formation of pseudomorphous GeSiSn layers directly on Si have been investigated. The transition from two-dimensional growth regime to three-dimensional of the GeSiSn film on Si(100) was studied for different mismatch with silicon and growth temperatures. A possibility of synthesis of multilayer structures by molecular beam epitaxy was shown. The crystal lattice constants were determined using the high-resolution transmission electron microscopy and X-ray diffractometry. The p-i-n-diodes based on multilayer GeSiSn/Si structures were created which demonstrated the photoresponse increasing by several orders of magnitude in comparison the Sn-free structures at an increase in the Sn content. Nanostructures based on GeSiSn layers have demonstrated the photoluminescence at 0.6−0.85 eV.

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Investigation of Sn surface segregation during GeSn epitaxial growth by Auger electron spectroscopy and energy dispersive x-ray spectroscopy

Cited by 48 publications

References 22 publications

Dislocation Pipe Diffusion and Solute Segregation during the Growth of Metastable GeSn

Dislocation Pipe Diffusion and Solute Segregation during the Growth of Metastable GeSn

Investigation of GeSn Strain Relaxation and Spontaneous Composition Gradient for Low-Defect and High-Sn Alloy Growth

PSEUDOMORPHIC GeSiSn LAYERS IN STRAINED HETEROSTRUCTURES

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