Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first-principles calculations

Murphy-Armando, Felipe

doi:10.1063/1.5117345

Cited by 12 publications

(9 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For electron transport, the conductivity tends to saturate for Si-rich alloys. This behavior has been found in many measurements of the electron Hall mobility of cubic Si 𝑥 Ge 1−𝑥 samples [60][61][62] and also in some calculations [56,63]. Due to disorder scattering in the random alloy, a minimum of the electrical conductivity near the middle of the composition range is expected.…”

Section: B Hexagonal Sige Alloyssupporting

confidence: 59%

“…For example, for cub-Ge, values of about −330 µV K −1 have been measured under normal conditions (𝜌 = 10 14 cm −3 ) [55]. Ab-initio calculations of 𝑛-doped cub-Ge gave values close to −270 µV K −1 (𝜌 = 1.1•10 19 cm −3 ) [56]. Calculations on 𝑛-doped Si nanosheets yielded values in the range of −300 to −500 µV K −1 (depending on the surface) with a similar range close to 300 to 500 µV K −1 for 𝑝-doped Si (both with 𝜌 = 1.1 • 10 19 cm −3 and 𝑇 = 300 K) [57].…”

Section: Seebeck Coefficientmentioning

confidence: 99%

See 1 more Smart Citation

Ensemble averages of ab initio optical, transport, and thermoelectric properties of hexagonal Si$_x$Ge$_{1-x}$ alloys

Borlido¹,

Bechstedt²,

Botti³

et al. 2022

Preprint

View full text Add to dashboard Cite

We present a comprehensive first-principles investigation of optical, transport, and thermoelectric properties of pure and doped hexagonal Si 𝑥 Ge 1−𝑥 alloys based on density-functional theory calculations, the Boltzmann transport equation, and the generalized quasi-chemical approximation to obtain alloy averages of electronic properties. At low temperature, phase decomposition into the hexagonal elementary crystals is thermodynamically favored, but around and above room temperature random alloys are predicted to be stable. While hexagonal Si has an indirect band gap, the gap of hexagonal Ge is direct with very weak optical transitions at the absorption edge. The alloy band gap remains direct for a Si content below 45 % and the oscillator strength of the lowest optical transitions is efficiently enhanced by alloying. The optical spectra show clear trends and both absorption edges and prominent peaks can be tuned with composition. The dependence of transport coefficients on carrier concentration and temperature is similar in cubic and hexagonal alloys. However, the latter display anisotropic response due to the reduced hexagonal symmetry. In particular, the transport mass exhibits a significant directional dependence. Seebeck coefficients and thermoelectric power factors of 𝑛-doped alloys show non-monotonous variations with the Si content independently of temperature.

show abstract

Section: B Hexagonal Sige Alloyssupporting

confidence: 59%

Section: Seebeck Coefficientmentioning

confidence: 99%

Ensemble averages of ab initio optical, transport, and thermoelectric properties of hexagonal Si$_x$Ge$_{1-x}$ alloys

Borlido¹,

Bechstedt²,

Botti³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…To date, Seebeck coefficients of Ge structures, and in particular Ge NWs, have not abounded in the literature. The Ge Seebeck coefficient has been evaluated at room temperature in the −600 to −1000 µV/K range [ 44 , 45 , 46 ] for bulk Ge for a low doping concentration and −400 µV/K for Ge thin films [ 46 ] but no value could be found for Ge NWs.…”

Section: Resultsmentioning

confidence: 99%

Imaging Thermoelectric Properties at the Nanoscale

et al. 2021

View full text Add to dashboard Cite

Based on our previous experimental AFM set-up specially designed for thermal conductivity measurements at the nanoscale, we have developed and validated a prototype which offers two major advantages. On the one hand, we can simultaneously detect various voltages, providing, at the same time, both thermal and electrical properties (thermal conductivity, electrical conductivity and Seebeck coefficient). On the other hand, the AFM approach enables sufficient spatial resolution to produce images of nanostructures such as nanowires (NWs). After a software and hardware validation, we show the consistency of the signals measured on a gold layer on a silicon substrate. Finally, we demonstrate that the imaging of Ge NWs can be achieved with the possibility to extract physical properties such as electrical conductivity and Seebeck coefficient, paving the way to a quantitative estimation of the figure of merit of nanostructures.

show abstract

“…[20,36] for strained Ge and SiGe. The effects of ionized impurity scattering are included using the Brooks-Herring approach [37][38][39][40]. To ease integration of the transport properties across the Brillouin zone at different strain conditions, we used the first-principles-based k•p analytic form of the electronic band structure of ε-Ge after Rideau et al [17].…”

Section: Calculation Of the Ge Electronic Transport Properties Under ...mentioning

confidence: 99%

Multivalley Electron Conduction at the Indirect-Direct Crossover Point in Highly Tensile-Strained Germanium

et al. 2022

Self Cite

View full text Add to dashboard Cite

As forward-looking electron devices increasingly adopt high-mobility, low-bandgap materials, such as germanium (Ge), questions remain regarding the feasibility of strain engineering in low-bandgap systems. Particularly, the Ge L-Γ valley separation (~150 meV) can be overcome by introducing a high degree of tensile strain (ε ≥ 1.5%). It is therefore essential to understand the nature of highly-strained Ge transport, wherein multi-valley electron conduction becomes a possibility. Here, we report on the competitiveness between L and Γ valley transport in highly tensile strained (ε ~ 1.6%) Ge/In 0.24 Ga 0.76 As heterostructures. Temperature-dependent magnetotransport analysis revealed two contributing carrier populations, identified as lower-and higher-mobility L and Γ valley electrons (in Ge) using temperature-dependent Boltzmann transport modeling. Coupling this interpretation with electron cyclotron resonance studies, the effective mass (m * ) of the higher-mobility Γ valley electrons was probed, revealing m * = (0.049 ± 0.007)m e . Moreover, comparison of the empirical and theoretical m * indicated that these electrons reside primarily in the first two quantum sublevels of the Ge Γ valley. Consequently, our results provide insight into the strain-dependent carrier dynamics of Ge, offering new pathways toward efficacious strain engineering.

show abstract

Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first-principles calculations

Cited by 12 publications

References 50 publications

Ensemble averages of ab initio optical, transport, and thermoelectric properties of hexagonal Si$_x$Ge$_{1-x}$ alloys

Ensemble averages of ab initio optical, transport, and thermoelectric properties of hexagonal Si$_x$Ge$_{1-x}$ alloys

Imaging Thermoelectric Properties at the Nanoscale

Multivalley Electron Conduction at the Indirect-Direct Crossover Point in Highly Tensile-Strained Germanium

Contact Info

Product

Resources

About