On the interplay between relaxation, defect formation, and atomic Sn distribution in Ge(1−x)Sn(x) unraveled with atom probe tomography

Kumar, Arul; Demeulemeester, Jelle; Bogdanowicz, Janusz; Bran, Julien; Melkonyan, Davit; Fleischmann, Claudia; Gencarelli, Federica; Shimura, Yosuke; Wang, W.; Loo, Roger; Vandervorst, Wilfried

doi:10.1063/1.4926473

Cited by 18 publications

(19 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Remarkably, no significant changes were detected in the (substitutional) Sn content and Sn distribution (Table I, Figure 1), in the layer strain or even in the molecular configuration (Figure 2) in this temperature range. This supports the recent findings 18 which showed that, contrary to the common belief, the Sn-cluster formation is not the main driving force for strain relaxation in the CVD-grown Ge 0.93 Sn 0.07 layers but solely a phenomenon occurring at the same time, governed by the thermodynamic solubility limit of Sn in Ge. The decoupling between strain relaxation and Snprecipitation was also verified in Ref.…”

Section: B Formation Of Surface Structures: Islands and Pitssupporting

confidence: 91%

“…Yet, it remains unclear whether these surface modifications are a kinetic pathway for phase separation and strain relaxation, 13 since Chen et al 14 did not observe any significant changes in the macroscopic strain level and only a minor reduction in the Sn concentration of the Ge 1-x Sn x film. Indeed, several authors 9,12,18 argue that the dominating mechanisms of strain relaxation in Ge 1-x Sn x alloys appear to be the formation of misfit dislocations rather than compositional or morphological instabilities, similar as in other group-IV alloys. 19 Clearly, we lack a comprehensive picture on the thermal stability and relaxation mechanisms, including both compositional and morphological changes in strained Ge 1-x Sn x films.…”

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Thermal stability and relaxation mechanisms in compressively strained Ge0.94Sn0.06 thin films grown by molecular beam epitaxy

Fleischmann

Lieten

Hermann

et al. 2016

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

Strained Ge 1-x Sn x thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro-and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge 0.94 Sn 0.06 films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge 0.94 Sn 0.06 films grown by molecular beam epitaxy.

show abstract

Section: B Formation Of Surface Structures: Islands and Pitssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

Thermal stability and relaxation mechanisms in compressively strained Ge0.94Sn0.06 thin films grown by molecular beam epitaxy

Fleischmann

Lieten

Hermann

et al. 2016

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Although the model proposed by Li et al 18 is consistent with the results of Kumar et al, 17 they provide no direct evidence that the relaxation takes place without Sn expulsion from the lattice and given Sn's low solubility in Ge, together with the non-equilibrium nature of the GeSn layers, it is surprising that Sn remains so firmly bound in the GeSn lattice during the relaxation process. In this regard, it should be noted that the use of XRD to determine both the substitutional Sn content and the elastic strain (relaxation) has a number of intrinsic limitations, namely (i) the technique averages over the depth probed, (ii) the values deduced depend on the validity of the model employed, and (iii) XRD provides information on the coherent parts of the sample while ignoring the disordered regions.…”

Section: Introductionmentioning

confidence: 75%

“…Upon annealing at 600 C they observed Sn precipitates on the surface of the GeSn layers. Recently, Kumar et al 17 used atom probe tomography to monitor Sn cluster formation during the GeSn layer relaxation. Although they found that Sn clusters formed during thermal anneals in the range of 580-640 C they could find no correlation between Sncluster formation and the degree of relaxation, which led them to conjecture that the main relaxation mechanism must a)…”

Section: Introductionmentioning

confidence: 99%

Interplay between relaxation and Sn segregation during thermal annealing of GeSn strained layers

Comrie

Mtshali

Sechogela

et al. 2016

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

The effect of thermal annealing on epitaxial GeSn (6.5% Sn) strained layers grown on Ge-buffered Si(100) wafers has been investigated using Rutherford backscattering spectrometry and X-ray diffraction to unambiguously determine the Sn substitutional content as well as the elastic strain in the layers. Vacuum annealing at temperatures below 400 C for 20 min has no noticeable effect on the strain in the epitaxial layers. Once the temperature was raised above 400 C, however, relaxation of the layer sets in and the GeSn layer has essentially completely relaxed following a 20 min anneal at 650 C. Using Rutherford backscattering and channelling spectrometry to provide compositional information as a function of depth enables one to monitor the effect of the thermal anneal on the Sn distribution throughout the layer, and also to directly extract their substitutional fraction (i.e., their solubility in the lattice). The results obtained show that when the relaxation initially sets in both the Ge and the Sn remain firmly bound in substitutional lattice sites and it is only around 600 C, and after substantial relaxation has taken place, that Sn is finally expelled from lattice sites and diffuses to the surface of the sample.

show abstract

“…c, A radial profile of the SiGe core/shell structure from the APT measurement integrated over a 1.0 µm length of the structure showing a Si content of around 25% as shown in (b). On the highlighted dotted rectangular volume of (c), we carry out a nearest neighbor analysis for Si atoms as previously used to evaluate random alloys of GeSn 45,46 . The nearest neighbor analysis evaluates the distances between each Si atoms pair and its first (to fourth) neighbors.…”

Section: Ab Initio Calculationsmentioning

confidence: 99%

Direct-bandgap emission from hexagonal Ge and SiGe alloys

Fadaly

Dijkstra

Suckert

et al. 2020

Nature

291

300

View full text Add to dashboard Cite

Silicon crystallized in the usual cubic (diamond) lattice structure has dominated the electronics industry for more than half a century. However, cubic silicon (Si), germanium (Ge) and SiGe-alloys are all indirect bandgap semiconductors that cannot emit light efficiently. Accordingly, achieving efficient light emission from group-IV materials has been a holy grail 1 in silicon technology for decades and, despite tremendous efforts 2-5 , it has remained elusive 6 . Here, we demonstrate efficient light emission from direct bandgap hexagonal Ge and SiGe alloys. We measure a sub nanosecond, temperature insensitive radiative recombination lifetime and observe a similar emission yield to direct bandgap III-V semiconductors. Moreover, we demonstrate how by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously tuned in a broad range, while preserving a direct bandgap. Our experimental findings are shown to be in excellent quantitative agreement with the ab initio theory. Hexagonal SiGe embodies an ideal material system to fully unite electronic and optoelectronic functionalities on a single chip, opening the way towards novel device concepts and information processing technologies.Silicon has been the workhorse of the semiconductor industry since it has many highly advantageous physical, electronic and technological properties. However, due to its indirect bandgap, silicon cannot emit light efficientlya property that has seriously constrained potential for applications to electronics and passive optical circuitry 7-9 . Silicon technology can only reach its full application potential when heterogeneously supplemented 10 with an efficient, direct bandgap light emitter.The band structure of cubic Si, presented in Fig. 1a is very well known, having the lowest conduction band (CB) minimum close to the X-point and a second lowest * These authors contributed equally to this work. † Correspondence to E.P.A.M.(e.p.a.m.bakkers@tue.nl).minimum at the L-point.As such, it is the archetypal example of an indirect bandgap semiconductor, that, notwithstanding many great efforts 3-6 , cannot be used for efficient light emission.By modifying the crystal structure from cubic to hexagonal, the symmetry along the 111 crystal direction changes fundamentally, with the consequence that the L-point bands are folded back onto the Γ-point. As shown in Fig. 1b, for hexagonal Si (Hex-Si) this results in a local CB minimum at the Γ-point, with an energy close to 1.7 eV 11-13 . Clearly, Hex-Si remains indirect since the lowest energy CB minimum is at the M-point, close to 1.1 eV. Cubic Ge also has an indirect bandgap but, unlike Si, the lowest CB minimum is situated at the L-point, as shown in Fig. 1c. As a consequence, for Hex-Ge the band folding effect results in a direct bandgap at the Γ-point with a magnitude close to 0.3 eV, as shown in the calculated band structure in Fig. 1d 14 .To investigate how the direct bandgap energy can be tuned by alloying Ge with Si, we calculated the band structures of He...

show abstract

On the interplay between relaxation, defect formation, and atomic Sn distribution in Ge(1−x)Sn(x) unraveled with atom probe tomography

Cited by 18 publications

References 17 publications

Thermal stability and relaxation mechanisms in compressively strained Ge0.94Sn0.06 thin films grown by molecular beam epitaxy

Thermal stability and relaxation mechanisms in compressively strained Ge0.94Sn0.06 thin films grown by molecular beam epitaxy

Interplay between relaxation and Sn segregation during thermal annealing of GeSn strained layers

Direct-bandgap emission from hexagonal Ge and SiGe alloys

Contact Info

Product

Resources

About