High Thermoelectric Power Factor Realization in Si-Rich SiGe/Si Superlattices by Super-Controlled Interfaces

• DOI: 10.1021/acsami.0c04982
• Publication Date: 2020-05-19T20:55:46Z
• Authors: Tatsuhiko Taniguchi; Takafumi Ishibe; Nobuyasu Naruse; Yutaka Mera; Md. Mahfuz Alam; Kentarou Sawano; Yoshiaki Nakamura
• Keywords: Realization (probability); Silicon-germanium

A Si-based superlattice is one of the promising thermoelectric films for realizing a stand-alone single-chip power supply. Unlike p-type (SL) achieving higher factor due to strain-induced high hole mobility, in n-type SL, strain can degrade lifting conduction band degeneracy. Here, we propose epitaxial Si-rich SiGe/Si SLs with ultrathin Ge segregation interface layers. The layers are designed be sufficiently strained, not give above Si Therein, drastic thermal conductivity reduction occurs by larger phonon scattering at interfaces large atomic size difference between and layers, while unstrained preserve degeneracy leading Seebeck coefficient. As result, Si0.7Ge0.3/Si SL controlled achieves ∼25 μW cm–1 K–2 in-plane direction room temperature, which superior ever reported SiGe-based films: SiGe films. also exhibits low ∼2.5 W m–1 K–1 cross-plane direction, ∼5 times lower than value conventional SL. These results demonstrate that differences bring breakthrough high-performance light-element-based