Effects of Iodine Doping on Electrical Characteristics of Solution-Processed Copper Oxide Thin-Film Transistors.

Hyeonju Lee,Bokyung Kim,Jaehoon Park,Xue Zhang,Jin-Hyuk Bae

doi:10.3390/ma14206118

Abstract

In order to implement oxide semiconductor-based complementary circuits, the improvement of the electrical properties of p-type oxide semiconductors and the performance of p-type oxide TFTs is certainly required. In this study, we report the effects of iodine doping on the structural and electrical characteristics of copper oxide (CuO) semiconductor films and the TFT performance. The CuO semiconductor films were fabricated using copper(II) acetate hydrate as a precursor to solution processing, and iodine doping was performed using vapor sublimated from solid iodine. Doped iodine penetrated the CuO film through grain boundaries, thereby inducing tensile stress in the film and increasing the film’s thickness. Iodine doping contributed to the improvement of the electrical properties of the solution-processed CuO semiconductor including increases in Hall mobility and hole-carrier concentration and a decrease in electrical resistivity. The CuO TFTs exhibited a conduction channel formation by holes, that is, p-type operation characteristics, and the TFT performance improved after iodine doping. Iodine doping was also found to be effective in reducing the counterclockwise hysteresis in the transfer characteristics of CuO TFTs. These results are explained by physicochemical reactions in which iodine replaces oxygen vacancies and oxygen atoms through the formation of iodide anions in CuO.

Highlights

Oxide semiconductors have been used as active channel materials in thin-film transistors (TFTs) owing to their excellent charge carrier mobility, high optical transmittance in the visible range, excellent chemical stability, and versatility in processing
We investigated the effects of iodine doping on the structural and electrical characteristics of p-type CuO semiconductors and the performance of CuO TFTs
This explains the improvement in the electrical properties of p-type CuO semiconductors through iodine doping, which, in turn, enhanced the TFT performance

Summary

Introduction

Oxide semiconductors have been used as active channel materials in thin-film transistors (TFTs) owing to their excellent charge carrier mobility, high optical transmittance in the visible range, excellent chemical stability, and versatility in processing. The local distribution of anisotropic oxygen 2p orbitals is a main factor in determining the valence band maximum of p-type oxide semiconductors, which results in large effective mass and low mobility for holes in p-type oxide semiconductors [8,9,10]. For this reason, a transparent p-type copper iodide (CuI) semiconductor has recently been proposed as a replacement for p-type oxide semiconductors [11]. To meet the demand for high-performance p-channel devices, Bae et al enhanced the performance of copper-based TFTs by doping the semiconductor film with gallium atoms to reduce oxygen vacancies, which are known to interfere with the conduction of hole carriers [14]. Research on doping technology for p-type oxide semiconductors is still in its infancy and doping these materials as a post-processing technology has hardly been studied

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Results

Conclusion