Electric Field Modulation of Giant Thermopower in Oxide Thin FilmTransistors and its Application for IR Sensor

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Top-gate type thin film transistor structure was fabricated on an oxide semiconductor, SrTiO3 single crystal plate. The electron transport and the thermopower S for the extremely thin two-dimensional electron gas, which can be formed on the SrTiO3 crystal by a gate voltage application, were precisely measured / analyzed. As a result of this study, followings were clarified. 1) Water incorporated nano-porous glass [CAN: H. Ohta et al., Nature Commun. 1: 118 (2010); Adv. Mater. 24, 740 (2012)] is very useful as a gate insulator. 2) Extremely thin 2DEG can be generated on the oxide semiconductor surface when ECBM of the oxide semiconductor is greater than EH2. 3) Extremely thin 2DEG (n3D >4×1021 cm-3) exhibited unusually large S-value, which is five times larger than that of bulk (Figure of merit, ZT~2). This clearly demonstrates that the transistor approach works well as the thermoelectric infrared sensor.