Improved Thermoelectric Power Factor of InGaZnO/SiO₂ Thin Film Transistor via Gate-Tunable Energy Filtering

Progress on improving the thermoelectric power factor (PF) of InGaZnO thin films by various surface treatment techniques has been seriously hindered by the innate coupled but opposing relationship between its electrical conductivity ( $\sigma _{{\mathrm {e}}}$ ) and Seebeck coefficient (S) . Therefore, proposing unique solutions to decouple these properties is crucial in advancing its thermoelectric performance. This study demonstrates that the ${S} - \sigma _{e}$ coupled relationship can be suppressed by integrating InGaZnO in an InGaZnO/SiO2 thin film transistor, leading to a significantly enhanced PF compared to pristine InGaZnO thin films. An exponential increase in $\sigma _{e}$ was observed without the typical severe decline in ${S}$ . An extremely narrow charge accumulation layer near the InGaZnO/SiO2 interface could have formed under a positive applied gate voltage ( ${V}_{G}$ ), causing a dramatic reduction of the thermoelectrically active region to an almost two-dimensional surface. By utilizing the Kamiya-Nomura percolation modeling, it was observed that energy filtering occurs at the InGaZnO/SiO2 interface. This likely causes a change in the shape of the potential barriers, which leads to the suppression of the ${S} - \sigma _{e}$ coupling relationship.