Enhanced electrical performance of InGaSnO thin-film transistors by designing a dual-active-layer structure

Abstract

In this study, dual-active-layer InGaSnO (IGTO) thin-film transistors (TFTs) were designed, and their electrical properties were investigated. Consequently, compared with the single-layer IGTO (pure Ar) TFTs, the dual-layer IGTO TFTs exhibited improved electrical properties, including a high field-effect mobility of 25.1 cm2 V−1 s−1, a low threshold voltage of 0.8 V, a high on/off current ratio of 1 × 108, a small subthreshold slope of 300 mV/decade, and a low off current. Additionally, the dual-layer IGTO TFTs showed superior stability for small Vth shifts of −1.9 V and 1.8 V under gate bias stress test conditions. Band structure analysis indicated that a thin front layer of IGTO (pure Ar) can provide an appropriate carrier concentration (Ne) near the IGTO (pure Ar)/IGTO (Ar/O2) interface, whereas a thick layer of IGTO (Ar/O2) can control the channel conductance and threshold voltage of IGTO TFTs. Moreover, atomic force microscopy, X-ray photoelectron spectroscopy, and Hall effect measurement results showed that the surface roughness, oxygen vacancies, Ne, and total trap density of IGTO (Ar/O2) films and TFTs were reduced by increasing the oxygen flow rate. Over all, the high performance dual-active-layer IGTO TFTs provides insights that can contribute to developing a new generation of transparent oxide thin-film electronics.