Layered topological semimetal GaGeTe: New polytype with non-centrosymmetric structure

Gallego-Parra, Samuel; Bandiello, Enrico; Liang, Akun; Silva, E. Lora da; Rodríguez‐Hernández, P.; Múñoz, A.; Radescu, S.; Romero, A. H.; Drašar, Č.; Errandonea, Daniel; Manjón, F. J.

doi:10.1016/j.mtadv.2022.100309

Cited by 8 publications

(9 citation statements)

References 79 publications

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“…Figure . 1a shows the variance of the Raman peak intensities with the incident light polarization which confirms the in-plane optical anisotropy of the GaGeTe flakes [20]. Additionally, the measured Raman peak positions are in agreement with other reports [19].…”

Section: A the Optical Parameters Of Gagetesupporting

confidence: 88%

“…It is worth noting that only non-centrosymmetric crystals exhibit the Pockels phenomenon. Recent studies on grown GaGeTe flakes demonstrated a noncentrosymmetric structure [19]. Another point to consider is the height difference between the Si waveguide and metal electrodes which induces a strain effect in the transferred GaGeTe.…”

Section: The Underlaying Eo Effects: Discussionmentioning

confidence: 99%

“…The GaGeTe crystals are part of the MXTe (M = Al, Ga; X = Si, Ge, Sn) 2D layered materials group which are made up of stacks of monolayers connected by weak van der Waals interactions [18]. Remarkably, recent studies on GaGeTe crystals identified their non-centrosymmetric structure [19].…”

Section: Introductionmentioning

confidence: 99%

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A Multi-layered GaGeTe Electro-Optic Device Integrated in Silicon Photonics

Tamalampudi

Dushaq

Villegas

et al. 2023

J. Lightwave Technol.

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Electrically tunable devices contribute significantly to key functions of photonics integrated circuits. Here, we demonstrate the tuning of the optical index of refraction based on hybrid integration of multilayered anisotropic GaGeTe on a silicon micro-ring resonator (Si-MRR). Under static applied (DC) bias and transverse-electric (TE) polarization, the device exhibits a linear resonance shift without any amplitude modulation. However, for the transverse-magnetic (TM) polarization, both amplitude and phase modulation is observed. The corresponding wavelength shift and half-wave voltage length product (𝑽 𝝅 . 𝒍) for the TE polarization are -1.78 pm/V and 0.9 V.cm, respectively.These values are enhanced for the TM polarizations and correspond to -6.65 pm/V and 0.28 V.cm, respectively. The dynamic radio frequency (RF) response of the devices was also tested at different bias conditions. Remarkably, the device exhibits a 1.6 MHz and 2.1 MHz response at 0 V and 7 V bias, respectively. Based on these findings, the integration of 2D GaGeTe on the silicon photonics platform has great potential for the next generation of integrated photonic applications such as switches and phase shifters.

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Section: A the Optical Parameters Of Gagetesupporting

confidence: 88%

Section: The Underlaying Eo Effects: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

A Multi-layered GaGeTe Electro-Optic Device Integrated in Silicon Photonics

Tamalampudi

Dushaq

Villegas

et al. 2023

J. Lightwave Technol.

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“…The conductivity effective mass was directly extracted from the BoltzTraP calculation using the following equation: 41 The band structure of the bulk GaGeTe was investigated using DFT calculations. Different theoretical methods such as PBE 44 and PBEsol 45 have been applied in previous reports, but the calculated band gaps are severely underestimated in comparison with an experimental value of ∼1 eV from the optical measurements. 30 In this study, we calculated the electronic structures by employing the TB-mBJ method, which is renowned for its capability of giving accurate band gaps for a wide range of semiconductors.…”

Section: Methodsmentioning

confidence: 99%

Layered GaGeTe Thermoelectric Materials with Multivalley Conduction Bands

Zhou,

Zhang,

Shen

et al. 2023

ACS Appl. Energy Mater.

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GaGeTe is interesting as a thermoelectric material since it has a layered tetradymite-like structure similar to state-of-the-art Bi2Te3. However, the electronic structure, electrical transport properties, and their rationalization in GaGeTe are rarely studied. In this study, we focus on the electronic structure and electrical transport properties of GaGeTe by combining theory and experiment. Experimentally, intrinsic p-type thermoelectric properties of pristine and Ag-doped GaGeTe polycrystalline samples are reported and found to be anisotropic due to the layered structure. Electronic structure calculation reveals GaGeTe as a semiconductor with a moderate band gap, consistent with the experimental transport properties showing no obvious bipolar effect. Based on the electronic structure, the Boltzmann transport theory is applied to calculate transport properties, leading to an excellent agreement with the experimental data of p-type GaGeTe. Strikingly, n-type electrical transport properties are predicted to be much more favorable than the p-type counterparts, which can be rationalized by the multivalley conduction bands with a primary contribution from a nontrivial 6-fold valley-degenerate conduction band. A peak zT of ∼0.7 at 800 K is estimated for n-type GaGeTe using the experimental lattice thermal conductivity of the pristine sample. We thereby expect GaGeTe to be a promising thermoelectric material if n-type doping is achievable. This work provides insights into the electronic structure and electrical transport for the further development of GaGeTe thermoelectrics.

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“…Germanium monoselenide (GeSe) has attracted great attention recently for optoelectronic and thermoelectric applications due to its excellent optoelectronic properties, − nontoxic and earth-abundant constituents, and rich crystal phases. GeSe usually crystallizes in five different substructures depending on the temperature and pressure conditions. ,− They are divided into two categories: three two-dimensional (2D) phases, defined as α, β, and γ, and two three-dimensional (3D) crystal structures. , Among these five allotropes, 2D α-GeSe in the orthorhombic space group Pnma is the most stable form with the lowest energy under ambient conditions (Table S1). Hence, α-GeSe has been the most intensively studied material in GeSe allotropes, being applied to various fields from solar cells with a certified efficiency of 5.2% to polarization-sensitive photodetectors with a remarkable dichroic ratio of 2.16 …”

Section: Introductionmentioning

confidence: 99%

Crystal Stability Determination of GeSe Allotropes

Miao

et al. 2023

J. Phys. Chem. C

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Germanium monoselenide (GeSe) has attracted increasing attention recently due to its rich polymorphism including stable room-temperature two-dimensional phases and metastable high-temperature three-dimensional phases that enable GeSe wide applications from optoelectronics to thermoelectrics. However, the relationship between the stability and crystal structure parameters such as bond length and angle is still unclear, where the rough cognition of a shorter covalent bond length is not enough to reveal the stability of crystal structures. Here, we introduce a method to evaluate the stability of five GeSe allotropes through bond and angle distortion metrics based on the stereoactivity of lone pairs existing on the Ge(II) atom. We find that the stereoactivity of lone pairs plays an important role in the bond composition. The stronger stereoactivity of lone pairs is enabled by the larger contribution of Ge 4s and 4p states on bond composition combined with the smaller contribution of Ge 4s to the antibonding orbital at valence band maximum. This thereby results in the stronger bonding strength with more distorted bond angles, finally enhancing the stability of phases.

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Layered topological semimetal GaGeTe: New polytype with non-centrosymmetric structure

Cited by 8 publications

References 79 publications

A Multi-layered GaGeTe Electro-Optic Device Integrated in Silicon Photonics

A Multi-layered GaGeTe Electro-Optic Device Integrated in Silicon Photonics

Layered GaGeTe Thermoelectric Materials with Multivalley Conduction Bands

Crystal Stability Determination of GeSe Allotropes

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