High-density carrier accumulation in ZnO field-effect transistors gated by electric double layers of ionic liquids

Hongtao Yuan, Hidekazu Shimotani, Atsushi Tsukazaki, Akira Ohtomo, Masashi Kawasaki, Yoshihiro Iwasa

Research output: Contribution to journalArticlepeer-review

505 Citations (Scopus)


Very recently, electric-field-induced superconductivity in art insulator was realized by timing charge carrier to a high density level (1 × 10 14 cm-2). To increase the maximum attainable carrier density for electrostatic tuning of electronic states in semiconductor field-effect transistors is a hot issue but a big challenge. Here, ultrahigh density carrier accumulation is reported, in particular at. low temperature, in a ZnO field-effect transistor gated by electric double layers of ionic liquid (IL). This transistor, called an electric double layer transistor (EDLT), is found to exhibit very high transconductance and an ultrahigh carrier density in a fast, reversible, and reproducible manner. The room temperature capacitance of EDLTs is found to be as large as 34 μF cm-2 deduced from Hall-effect measurements, and is mainly responsible for the carrier density modulation in a very wide range. Importantly, the IL dielectric, with a supercooling property, Is found to have charge-accumulation capability even at low temperatures, reaching an ultrahigh carrier density of 8×10 14cm-2at 220K and maintaining a density of 5.5×1014 cm-2 1.8K. This high carrier density of EDLTs is of great importance not only in practical device applications but also in fundamental research; for example, in the search for novel electronic phenomena, such as superconductivity, In oxide systems.

Original languageEnglish
Pages (from-to)1046-1053
Number of pages8
JournalAdvanced Functional Materials
Issue number7
Publication statusPublished - 2009 Apr 9


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