Despite being a fundamental electronic component for over 70 years, it is still possible to develop different transistor designs, including the addition of a diode-like Schottky source electrode to thin-film transistors. The discovery of a dependence of the source barrier height on the semiconductor thickness and derivation of an analytical theory allow us to propose a design rule to achieve extremely high voltage gain, one of the most important figures of merit for a transistor. Using an oxide semiconductor, an intrinsic gain of 29,000 was obtained, which is orders of magnitude higher than a conventional Si transistor. These same devices demonstrate almost total immunity to negative bias illumination temperature stress, the foremost bottleneck to using oxide semiconductors in major applications, such as display drivers. Furthermore, devices fabricated with channel lengths down to 360 nm display no obvious short-channel effects, another critical factor for high-density integrated circuits and display applications. Finally, although the channel material of conventional transistors must be a semiconductor, by demonstrating a high-performance transistor with a semimetal-like indium tin oxide channel, the range and versatility of materials have been significantly broadened.

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Low operating voltages have been long desired for thin-film transistors (TFTs). However, it is still challenging to realise 1-V operation by using conventional dielectrics due to their low gate capacitances and low breakdown voltages. Recently, electric double layers (EDLs) have been regarded as a promising candidate for low-power electronics due to their high capacitance. In this work, we present the first sputtered SiO2 solid-state electrolyte. In order to demonstrate EDL behaviour, a sputtered 200 nm-thick SiO2 electrolyte was incorporated into InGaZnO TFTs as the gate dielectric. The devices exhibited an operating voltage of 1 V, a threshold voltage of 0.06 V, a subthreshold swing of 83 mV dec−1 and an on/off ratio higher than 105. The specific capacitance was 0.45 µF cm−2 at 20 Hz, which is around 26 times higher than the value obtained from thermally oxidised SiO2 films with the same thickness. Analysis of the microstructure and mass density of the sputtered SiO2 films under different deposition conditions indicates that such high capacitance might be attributed to mobile protons donated by atmospheric water. The InGaZnO TFTs with the optimised SiO2 electrolyte also showed good air stability. This work provides a new pathway to the realisation of high-yield low-power electronics.

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