Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

Gencarelli, Federica; Shimura, Yosuke; Kumar, Arul; Vincent, Benjamin; Moussa, Alain; Vanhaeren, Danielle; Richard, Olivier; Bender, Hugo; Vandervorst, Wilfried; Caymax, Matty; Loo, Roger; Heyns, Marc

doi:10.1016/j.tsf.2015.07.076

Cited by 12 publications

(12 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This situation results in weaker and broader averaged signals as compared to the strong sharp peaks expected for ideal perfect materials. Such disorder is especially significant in the localized amorphous Ge 1Àx Sn x regions 27 present in the investigated layers (as confirmed by TEM inspection 27 ). In fact, amorphous regions likely contain several different configurations corresponding to very weak EXAFS signals.…”

Section: -7supporting

confidence: 54%

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Gencarelli

Grandjean

Shimura

et al. 2015

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

We present an extended X-ray absorption fine structure investigation of the local environment of Sn atoms in strained and relaxed Ge1−xSnx layers with different compositions. We show that the preferred configuration for the incorporation of Sn atoms in these Ge1−xSnx layers is that of a α-Sn defect, with each Sn atom covalently bonded to four Ge atoms in a classic tetrahedral configuration. Sn interstitials, Sn-split vacancy complexes, or Sn dimers, if present at all, are not expected to involve more than 2.5% of the total Sn atoms. This finding, along with a relative increase of Sn atoms in the second atomic shell around a central Sn atom in Ge1−xSnx layers with increasing Sn concentrations, suggests that the investigated materials are homogeneous random substitutional alloys. Within the accuracy of the measurements, the degree of strain relaxation of the Ge1−xSnx layers does not have a significant impact on the local atomic surrounding of the Sn atoms. Finally, the calculated topological rigidity parameter a** = 0.69 ± 0.29 indicates that the strain due to alloying in Ge1−xSnx is accommodated via bond stretching and bond bending, with a slight predominance of the latter, in agreement with ab initio calculations reported in literature.

show abstract

Section: -7supporting

confidence: 54%

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Gencarelli

Grandjean

Shimura

et al. 2015

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…The major challenges towards the fabrication of high-quality strain-free GeSn alloys with high Sn content are attributed to: (i) extremely low equilibrium solubility of α-Sn in Ge (<1%) [16], and as a consequence, a nonequilibrium epitaxy process is required to prevent the Sn segregation and the allotropic phase transition between α-Sn and β-Sn; (ii) due to the 15% lattice mismatch between Ge (6.489 Å) and α-Sn (5.646 Å), the high compressive strains arise during epitaxial growth, making it difficult to grow a relaxed and defect-free thin film of GeSn on Ge-buffered Si wafers; and (iii) low temperature is required for GeSn epitaxy to prevent Sn precipitation, the formation of dislocations and point defects. On the other hand, a low-temperature process leads to the formation of localized or extended amorphous inclusions and a significantly roughened surface [17]. Commonly, the GeSn epitaxial layers are characterized by a high density of misfit dislocations (MDs) at the GeSn/Ge interface [18,19] and Sn segregation at the surface of GeSn films [20,21].…”

Section: Introductionmentioning

confidence: 99%

Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films

Кондратенко

Derenko

Mazur

et al. 2020

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

We report the results of a study that was conducted to investigate the recombination paths of photoexcited charge carriers in GeSn thin films. The charge carrier lifetime was predicted as a function of temperature from a description of photoconductivity transients, assuming co-influence of Shockley–Read–Hall and radiative carrier recombination paths. We identify that dislocations are the source of a band of electronic states with the highest occupied state at E V + (85÷90) meV that acts as Shockley–Read–Hall centers determining the charge carrier lifetime. The photoluminescence (PL) and photoconductivity spectroscopy have been applied to distinguish between the contribution of both band-to-band and dislocation-related electron transitions. The PL band was found to demonstrate a low-energy shift of about 80 ± 20 meV relative to the edge of the photoconductivity spectra in the indirect bandgap GeSn films with dislocations. The role of a different nature deeper acceptor level at E V + (140 ÷ 160) meV in the recombination processes of the GeSn layers with better structural quality and the Sn content higher than 4% was discussed. This detailed understanding of the recombination processes is of critical importance for developing GeSn/Ge-based optoelectronic devices.

show abstract

“…Two commercially available Ge precursors, germane (GeH 4 ) and digermane (Ge 2 H 6 ), are commonly used in (Si)GeSn chemical vapor deposition (CVD) reactors, while SnCl 4 is the precursor of choice for the Sn atoms. The increased reactivity of Ge 2 H 6 at low growth temperatures and the resulting high growth rates makes it ideal for the epitaxy of thick relaxed layers. , However, Ge 2 H 6 is significantly more expensive than GeH 4 , has limited availability, and the films may be accompanied by the formation of defects. − On the other hand, GeH 4 offers lower growth rates and a narrower window of the growth parameters, like the reactor pressure, gas flow rates, and temperature, which offers high crystallinity Sn-rich Ge 1– x Sn x alloys. , It then becomes clear that these parameters have a strong impact on the gas phase reactions of different molecules like GeH 4 and Ge 2 H 6 . The preferred reaction partner for the stable SnCl 4 molecule on the substrate surface are GeH x ( x = 1,2,3) radicals.…”

Section: Introductionmentioning

confidence: 99%

Isothermal Heteroepitaxy of Ge_1–xSn_x Structures for Electronic and Photonic Applications

Concepción

Søgaard

Bae

et al. 2023

ACS Appl. Electron. Mater.

View full text Add to dashboard Cite

Epitaxy of semiconductor-based quantum well structures is a challenging task since it requires precise control of the deposition at the submonolayer scale. In the case of Ge1–x Sn x alloys, the growth is particularly demanding since the lattice strain and the process temperature greatly impact the composition of the epitaxial layers. In this paper, the realization of high-quality pseudomorphic Ge1–x Sn x layers with Sn content ranging from 6 at. % up to 15 at. % using isothermal processes in an industry-compatible reduced-pressure chemical vapor deposition reactor is presented. The epitaxy of Ge1–x Sn x layers has been optimized for a standard process offering a high Sn concentration at a large process window. By varying the N2 carrier gas flow, isothermal heterostructure designs suitable for quantum transport and spintronic devices are obtained.

show abstract

Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

Cited by 12 publications

References 26 publications

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films

Isothermal Heteroepitaxy of Ge_1–xSn_x Structures for Electronic and Photonic Applications

Contact Info

Product

Resources

About

Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

Cited by 12 publications

References 26 publications

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films

Isothermal Heteroepitaxy of Ge1–xSnx Structures for Electronic and Photonic Applications

Contact Info

Product

Resources

About

Isothermal Heteroepitaxy of Ge_1–xSn_x Structures for Electronic and Photonic Applications