The thermoelectric properties of Ge/SiGe modulation doped superlattices

Samarelli, Antonio; Llin, Lourdes Ferre; Cecchi, Stefano; Frigerio, Jacopo; Etzelstorfer, Tanja; Müller, E.; Zhang, Y.; Watling, J.R.; Chrastina, D.; Isella, Giovanni; Stangl, J.; Hague, J. P.; Weaver, John; Dobson, Phillip S.; Paul, Douglas J.

doi:10.1063/1.4811228

Cited by 73 publications

(70 citation statements)

References 53 publications

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“…Since the PF is defined by α 2 σ, this increased by a factor of 2.1 reaching a maximum value of 1.34 mWK -2 m -1 for a doping density of 2.0x10 18 cm -3 . This result is very modest compared to the in-plane values [16], and even smaller than PF for p-Ge material reported in the literature [21]. The main difference was due to the small σ values obtained in the cross-plane direction, which were expected to be 7 or 8 times smaller than the in-plane electrical conductivities, as it is shown in Table 1.…”

Section: Results and Conclusioncontrasting

confidence: 52%

“…The measured thermoelectric cross-plane properties for SL1, SL2 and SL3 are shown in Table 1, and they are compared to p-Ge bulk material [21] and to in-plane values for Ge/Si 0.3 Ge 0.7 superlattices (previous work published in [16]). …”

Section: Results and Conclusionmentioning

confidence: 99%

“…[14,16] XRD reciprocal space maps along the (004) and (224) Bragg reflections indicated that all the superlattices were strain symmetrized to the relaxed virtual substrates. The measurements were performed using a PANalytical X'Pert PRO MRD highresolution X-ray diffractometer: the system is equipped with a hybrid mirror and 2-bounce asymmetric Ge monochromator.…”

Section: Design and Growthmentioning

confidence: 99%

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Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

et al. 2016

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-Silicon and germanium materials have demonstrated an increasing attraction for energy harvesting, due to their sustainability and integrability with complementary metal oxide semiconductor and micro-electro-mechanical-systems technology. The thermoelectric efficiencies for these materials, however, are very poor at room temperature and so it is necessary to engineer them in order to compete with telluride based materials, which have demonstrated at room temperature the highest performances in literature [1].Micro-fabricated devices consisting of mesa structures with integrated heaters, thermometers and Ohmic contacts were used to extract the cross-plane values of the Seebeck coefficient and the thermal conductivity from p-and n-Ge/Si x Ge 1-x superlattices. A second device consisting in a modified circular transfer line method structure was used to extract the electrical conductivity of the materials. A range of p-Ge/Si 0.5 Ge 0.5 superlattices with different doping levels was investigated in detail to determine the role of the doping density in dictating the thermoelectric properties. A second set of n-Ge/Si 0.3 Ge 0.7 superlattices was fabricated to study the impact that quantum well thickness might have on the two thermoelectric figures of merit, and also to demonstrate a further reduction of the thermal conductivity by scattering phonons at different wavelengths. This technique has demonstrated to lower the thermal conductivity by a 25% by adding different barrier thicknesses per period.

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Section: Results and Conclusioncontrasting

confidence: 52%

Section: Results and Conclusionmentioning

confidence: 99%

Section: Design and Growthmentioning

confidence: 99%

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Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

et al. 2016

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“…Пропонувались різні способи зменшення теплопровідності структур Si 1-x Ge x , що включали наноструктурування матеріалу, використання Si/Ge надрешіток, зміни їх композиційного складу [8]. Альтернативним способом збільшення термоелектричної добротності Si 1-x Ge x розглядається використання структур з неоднорідним розподілом легуючих домішок, а саме -модульовано легованих плівок SiGe [9]. Розсіювання фононів на неоднорідно розподілених легуючих домішках, зокрема, фосфору чи бору, зумовлює зменшення теплопровідності робочого матеріалу, результатом чого є збільшення термоелектричної добротності.…”

Section: вступunclassified

Calculations of the thermal conductivity of Si1-xGex films with nonuniform composition

Kuryliuk

Krit

2018

PCSS

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SiGe films have attracted much attention recently due to experimental demonstrations of improved thermoelectric properties over those of the corresponding bulk material. However, despite this increasing attention, available information on the thermoelectric properties of Si1-xGex films is quite limited, especially for nonuniform composition in wide temperature interval. In this paper we have used the Boltzmann equation under the relaxation-time approximation to calculate the thermal conductivity of Si1-xGex films with nonuniform composition. It is confirmed that SiGe films with nonuniform composition has significantly lower thermal conductivity than its uniform counterpart. This suggests that an improvement in thermoelectric properties is possible by using the SiGe films with nonuniform distribution of germanium.

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“…A recent typical work on Si 1−x Ge x TE films was carried out by Samarelli et al, 19) which involved the preparation of high-performance Si 1−x Ge x superlattice films by metal organic chemical vapor deposition (MOCVD) and plasmaenhanced chemical vapor deposition (PECVD). The superlattice films showed the maximum power factor of 6 × 10 −3 W·m −1 ·K −2 and the minimum thermal conductivity of 4.5 W·m −1 ·K −1 achieved by PECVD.…”

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confidence: 99%

Improved thermoelectric property of B-doped Si/Ge multilayered quantum dot films prepared by RF magnetron sputtering

Peng

Liu

et al. 2017

Jpn. J. Appl. Phys.

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The use of nanostructured thermoelectric materials that can effectively reduce the lattice conductivity with minimal effects on electrical properties has been recognized as the most successful approach to decoupling three key parameters (S, σ, and κ) and reaching high a dimensionless figure of merit (ZT ) values. Here, five-period multilayer films consisting of 10 nm B-doped Si, 1.1 nm B, and 13 nm B-doped Ge layers in each period were prepared on Si wafer substrates using a magnetron sputtering system. Nanocrystallites of 22 nm diameter were formed by post-annealing at 800 °C in a short time. The nanostructures were confirmed by X-ray diffraction analysis, Raman spectroscopy, and transmission electron microscopy. The maximum Seebeck coefficient of Si/Ge films is significantly increased to 850 µV/K at 200 °C with their electrical resistivity decreased to 1.3 ' 10 %5 Ω&m, and the maximum power factor increased to 5.6 ' 10 %2 W&m %1 &K %2 . The improved thermoelectric properties of Si/Ge nanostructured films are possibly attributable to the synergistic effects of interface scattering, interface barrier, and quantum dot localization.

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The thermoelectric properties of Ge/SiGe modulation doped superlattices

Cited by 73 publications

References 53 publications

Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

Calculations of the thermal conductivity of Si1-xGex films with nonuniform composition

Improved thermoelectric property of B-doped Si/Ge multilayered quantum dot films prepared by RF magnetron sputtering

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