Next Generation Device Grade Silicon-Germanium on Insulator

Littlejohns, Callum G.; Nedeljkovic, Milos; Mallinson, Christopher F.; Watts, John F.; Mashanovich, Goran Z.; Reed, Graham T.; Gardes, Frederic Y.

doi:10.1038/srep08288

Cited by 53 publications

(40 citation statements)

References 35 publications

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“…3a) are clearly delineated by abrupt orientation changes in the dendrites and regions of high-germanium content that solidify at the termination of each grain. The latter are similar to the Ge-rich terminal caps in nanowires51 and microencapsulated SiGe films30. The orientation of an unusually long dendrite can be seen to vary several degrees over a length of ∼1 mm.…”

Section: Resultsmentioning

confidence: 59%

“…This would permit direct integration of high-mobility circuit elements30 with minimal germanium concentration gradients and reduced heating of the wafer, in a two-dimensional equivalent of our process.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, in an alloy system, non-uniform composition could lead to excess scattering due to the refractive index variations. Rapid thermal annealing and related techniques28 have been used to crystallize insulator-encapsulated alloy thin2930 and thick31 films, and similar processing has been shown to improve overall crystallinity of semiconductor core fibres32. Laser processing, for which the fibre geometry is particularly well suited, as established in the case of conventional glass fibres333435, combines a small heat zone and large thermal gradients with fine motion and temperature control.…”

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confidence: 99%

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Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

et al. 2016

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Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO 2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core.

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Section: Resultsmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

et al. 2016

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“…As a result, components of the core intermix during fiber drawing or breakup, and the initial core structure is lost. Another route needs to be used to go beyond those limitations.The solidification of SiGe and pure silicon and germanium has been the subject of a large number of studies in different types of configurations and geometries (16)(17)(18)(19)(20). First of all, both the alloy and pure materials are known to expand upon solidification, owing to their diamond cubic structure, such that constrained solidification should be associated with pressure buildup.…”

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confidence: 99%

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

Gumennik

Levy

Grena

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes. We first produce an array of silicon−germanium particles embedded in silica, through capillary breakup of an alloy-core silica-cladding fiber. Heating and subsequent controlled cooling of individual particles with a two-wavelength laser setup allows us to realize two different morphologies, the first being a silicon−germanium compositionally segregated Janus particle oriented with respect to the illumination axis and the second being a sphere made of dendrites of germanium in silicon. Gigapascal-level compressive stresses are measured within pure silicon solidified in silica as a direct consequence of volume-constrained solidification of a material undergoing anomalous expansion. The ability to generate microspheres with controlled morphology and unusual stresses could pave the way toward advanced integrated in-fiber electronic or optoelectronic devices. multimaterial fibers | microparticles | confined solidification | silicon−germanium spheres | stressed silicon C ontrolling the microstructure or state of stress of microparticles and nanoparticles is often key to attaining the desired properties for a specific application (1-5); however, the ability to do so is strongly limited by the synthesis method. For instance, nonspherically symmetric distributions of inorganic materials are difficult to achieve from bottom-up approaches (4-7). Likewise, controlling the state of stress or strain of semiconductor particles is challenging in unconstrained nucleation-and-growth synthesis methods. However, Janus particles of silicon−germanium (SiGe) could potentially find applications as microswimmers or nanoswimmers owing to asymmetric absorption properties (8), as well as in infrared photodetectors or solar cells for increased infrared absorption (9). Stressed silicon particles, on the other hand, could be used for bandgap tunability in photonic or optoelectronic devices (10-12).In the past few years, thermally drawn multimaterial fibers have emerged as a unique platform for top-down scalable fabrication of microparticles to nanoparticles over a broad range of materials, through controlled in-fiber capillary breakup of the fiber components (13-15). In the case of polymers or chalcogenide glasses, structural control of the particle can be achieved by constructing complex cores at the preform level, which is later broken up in the fiber state to form structured particles (13). However, in the case of traditional semiconductor materials such as silicon and germanium, the same...

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“…An ultrathin SiGe-on-insulator (SGOI) layer is essential to fabricate the SiGe nanowire by lithographic technology. In the field of ULSI devices, such as a metal-oxide-semiconductor transistor, there are a variety of fabrication methods of single-crystalline SiGe (sc-SiGe) thin film grown on SiO 2 /Si substrates [24][25][26][27][28][29][30][31][32]. Most of them are difficult and costly since their process is complicated and is not fit for a large-area formation.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of ultrathin poly-crystalline SiGe-on-insulator layer for thermoelectric applications

et al. 2019

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For realizing high power generator efficiency based on thermoelectricity, Si, Ge and SiGe nanostructures have attracted attention. In this paper, we have investigated a new approach to fabricate an ultrathin polycrystalline SiGe-on-insulator (pc-SGOI) substrate by a simple process based on Si and Ge deposition followed by thermal diffusion suitable for thermoelectric devices. A 45-nmthick SGOI layer with a Ge fraction of nearly 0.45 was fabricated, and the Ge fraction was homogeneous in plane over the layer. Its thermal conductivity was 0.87 W mK −1 , lower than that of a single-crystalline SGOI layer. This is caused by the enhancement of scattering of phonons at grain boundaries in the pc-SGOI layer.

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Next Generation Device Grade Silicon-Germanium on Insulator

Cited by 53 publications

References 35 publications

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

Laser recrystallization and inscription of compositional microstructures in crystalline SiGe-core fibres

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

Fabrication of ultrathin poly-crystalline SiGe-on-insulator layer for thermoelectric applications

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