Performance and reliability improvement of all-solution processed indium zinc oxide thin-film transistor by UV irradiation treatment

Abstract

Developing a low-temperature fabrication strategy for amorphous oxide semiconductors, such as amorphous indium zinc oxide (a-IZO) channel layers, for use in flexible oxide-based thin-film transistors (TFTs) is essential. In this work, high-performance and highly stable all-solution processed a-IZO TFTs were achieved by varying the duration of a photo-assisted combination treatment (UV combination treatment), which combines UV irradiation with a low heating temperature (115 °C) in an all-solution processed approach. From the experimental results, UV irradiation can activate the IZO source, drain, and gate electrodes which induces TFT switching. X-ray photoelectron spectroscopy analysis revealed oxygen vacancy (V o) generation after the UV combination treatment which increased the carrier concentration and improved the conductivity of IZO. All-solution processed a-IZO TFTs with high performance and stability, high mobility (µ) up to 17.45 cm2 V−1 s−1, threshold voltage (Vth) = −1.2 V, and subthreshold swing (SS) = 0.64 V dec−1, were obtained at a low temperature of 115 °C for 90 min treatment time. The stability behavior of self-aligned top-gate, top-contact a-IZO TFT fabricated by UV combination treatment was investigated under positive bias stress (PBS) and negative bias stress (NBS) with the smallest ΔV th of 2.4 V and 0.5 V for PBS and NBS, respectively. Our work shows that better stability indicated by the smaller ΔV th is achieved due to reduction of interface trap density and moisture-related impurities, in particular on the activated electrode area. As a result, it can be inferred that UV combination treatment is a simple and promising method to enhance the electrical and stability performance of a-IZO TFTs even with the low-temperature process, which is useful for flexible devices.