Boosting Modulation of Oxide Semiconductors via Voltage-Based Ambi-Ionic Migration

In recent years, high-performance amorphous oxide semiconductor thin-film transistor (AOS TFT) technology is required to meet the increasing demand for novel displays, such as rollable, transparent, or augmented reality head-up displays. It has been demonstrated that voltage-based modulation techniques for AOS-based active layers can achieve high-performance AOS TFTs. The voltage-based modulation technique allows specific ions to migrate into the active layer depending on the polarity of the applied voltage, thus easily modulating the active layer. Additionally, potassium superoxide (KO2) solution is employed in AOS TFTs as a source of potassium (K+) and highly reactive superoxide radical (O2•–) ions. The K+ and O2•– ions in the KO2 solution are controlled by an applied voltage bias and rapidly migrate into the active layer, directly changing its chemical composition and electrical properties. AOS TFTs that use this technique exhibit better electrical performance than conventional AOS TFTs: the field-effect mobility improved from 10.05 to 15.31 cm2/V·s; the subthreshold swing decreased from 0.44 to 0.33 V/dec; the Ion/off ratio increased from 1.24 × 107 to 3.17 × 108; and the threshold voltage shift decreased from 5.2 to 3.4 V under a positive bias stress test conducted over 10 000 s. Ultimately, this approach to modulating the internal ion distribution in oxide semiconductors could provide opportunities for various AOS devices to attain desirable electrical characteristics.