2020年6月3日
High Thermoelectric Power Factor Realization in Si-Rich SiGe/Si Superlattices by Super-Controlled Interfaces
ACS Applied Materials and Interfaces
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- 巻
- 12
- 号
- 22
- 開始ページ
- 25428
- 終了ページ
- 25434
- 記述言語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1021/acsami.0c04982
A Si-based superlattice is one of the promising thermoelectric films for realizing a stand-alone single-chip power supply. Unlike a p-type superlattice (SL) achieving a higher power factor due to strain-induced high hole mobility, in the n-type SL, the strain can degrade the power factor due to lifting conduction band degeneracy. Here, we propose epitaxial Si-rich SiGe/Si SLs with ultrathin Ge segregation interface layers. The ultrathin interface layers are designed to be sufficiently strained, not to give strain to the above Si layers. Therein, a drastic thermal conductivity reduction occurs by larger phonon scattering at the interfaces with the large atomic size difference between Si layers and Ge segregation layers, while unstrained Si layers preserve a high conduction band degeneracy leading to a high Seebeck coefficient. As a result, the n-type Si0.7Ge0.3/Si SL with controlled interfaces achieves a higher power factor of ∼25 μW cm-1 K-2 in the in-plane direction at room temperature, which is superior to ever reported SiGe-based films: SiGe-based SLs and SiGe films. The Si0.7Ge0.3/Si SL with controlled interfaces also exhibits a low thermal conductivity of ∼2.5 W m-1 K-1 in the cross-plane direction, which is ∼5 times lower than the reported value in a conventional Si0.7Ge0.3/Si SL. These results demonstrate that strain and atomic differences controlled by ultrathin layers can bring a breakthrough for realizing high-performance light-element-based thermoelectric films.
- リンク情報
- ID情報
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- DOI : 10.1021/acsami.0c04982
- ISSN : 1944-8244
- eISSN : 1944-8252
- PubMed ID : 32427454
- SCOPUS ID : 85086052102