Enhancing the Seebeck effect in Ge/Si through the combination of interfacial design features

Abstract

Due to their inherent physical properties, thin-film Si/SiGe heterostructures have specific thermal management applications in advanced integrated circuits and this in turn is essential not only to prevent a high local temperature and overheat inside the circuit, but also generate electricity through the Seebeck effect. Here, we were able to enhance the Seebeck effect in the germanium composite quantum dots (CQDs) embedded in silicon by increasing the number of thin silicon layers inside the dot (multi-fold CQD material). The Seebeck effect in the CQD structures and multi-layer boron atomic layer-doped SiGe epitaxial films was studied experimentally at temperatures in the range from 50 to 300 K and detailed calculations for the Seebeck coefficient employing different scattering mechanisms were made. Our results show that the Seebeck coefficient is enhanced up to ≈40% in a 3-fold CQD material with respect to 2-fold Ge/Si CQDs. This enhancement was precisely modeled by taking into account the scattering of phonons by inner boundaries and the carrier filtering by the CQD inclusions. Our model is also able to reproduce the observed temperature dependence of the Seebeck coefficient in the B atomic layer-doped SiGe fairly well. We expect that the phonon scattering techniques developed here could significantly improve the thermoelectric performance of Ge/Si materials through further optimization of the layer stacks inside the quantum dot and of the dopant concentrations.

Synthesis and Properties of Bismuth Selenide Based Nanolaminates for Application in Thermoelectrics

“…Most likely, the increase of the Seebeck coefficient is related to the phonon scattering and carrier filtering at the inner interfaces between the layers in the nanolaminates. [ 34 ] Simultaneously, the resistivity of the Bi 2 Se 3 :Sn nanolaminate increased by ≈2 times, while the resistivity of the Bi 2 Se 3 :Te nanolaminate decreased by approximately five times in comparison with single doped films (Table 1). Increase of the resistivity of the Bi 2 Se 3 :Sn nanolaminate presumably may be related to the significant electrical resistance of grain and interlayer boundaries in it.…”

The effect of electron–phonon and electron-impurity scattering on the electronic transport properties of silicon/germanium superlattices

“…The effect of such coupled electron-phonon dynamics on the thermoelectric properties of silicon has recently received renewed attention. 43,68,72 Several phonon engineering strategies have been proposed to improve S with nanostructuring; 43,73 however, contradictory results have been reported. 74,75 To accurately account for the effect of phonon engineering approaches on electronic transport properties, one needs to solve the coupled BTE's for electrons and phonons, which makes it especially challenging for SL nanostructures, where phonons are strongly affected and might deviate from the bulk character.…”

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

“…At present, vapor-phase approaches are generally found not suitable for the synthesis of high-quality nanocrystals due to existing limitations found in instruments and precursors [76][77][78]. In contrast, the liquid-phase colloidal synthesis of monodisperse semiconductor nanocrystals can offer a convenient route towards low-cost and scalable low-dimensional TE materials.…”