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arXiv · 1112.2030

Unusually large enhancement of thermopower in an electric field induced two-dimensional electron gas

Hiromichi Ohta·Taku Mizuno·Shijian Zheng·Takeharu Kato·Yuichi Ikuhara·Katsumi Abe·Hideya Kumomi·Kenji Nomura·Hideo Hosono
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Abstract

Two-dimensionally confined electrons showing unusually large thermopower (S) have attracted attention as a potential approach for developing high performance thermoelectric materials. However, enhanced S has never been observed in electric field induced two-dimensional electron gas (2DEG). Here we demonstrate electric field modulation of S for a field effect transistor (FET) fabricated on a SrTiO3 crystal using a water-infiltrated nanoporous glass as the gate insulator. An electric field application confined carrier electrons up to ~2E15 /cm^2 in an extremely thin (~2 nm) 2DEG. Unusually large enhancement of |S| was observed when the sheet carrier concentration exceeded 2.5E14 /cm^2, and it modulated from ~600 (~2E15 /cm^2) to ~950 μV/K (~8E14 /cm^2), which were approximately five times larger than those of the bulk, clearly demonstrating that an electric field induced 2DEG provides unusually large enhancement of |S|.

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Hiromichi Ohta, Taku Mizuno, Shijian Zheng, Takeharu Kato, Yuichi Ikuhara, Katsumi Abe, Hideya Kumomi, Kenji Nomura, Hideo Hosono. 2011-12-13. Unusually large enhancement of thermopower in an electric field induced two-dimensional electron gas. https://doi.org/10.1002/adma.201103809

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