| AVS 57th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuP |
| Session: | Applied Surface Science Poster Session |
| Presenter: | S. Heo, Samsung Advanced Institute of Technology, Korea |
| Authors: | S. Heo, Samsung Advanced Institute of Technology, Korea J.G. Chung, Samsung Advanced Institute of Technology, Korea H.I. Lee, Samsung Advanced Institute of Technology, Korea E.H. Lee, Samsung Advanced Institute of Technology, Korea J.C. Lee, Samsung Advanced Institute of Technology, Korea G.S. Park, Samsung Advanced Institute of Technology, Korea J.S. Oh, Dongguk University, Korea H.Y. Cho, Dongguk University, Korea D. Tahi, Chungbuk National University, Korea L.S. Son, Chungbuk National University, Korea S.K. Oh, Chungbuk National University, Korea H.J. Kang, Chungbuk National University, Korea T. Nagatomi, Osaka University, Japan Y. Takai, Osaka University, Japan |
| Correspondent: | Click to Email |
Transparent oxide conductor and semiconductor are useful for us to develop electronic components in various applications such as flat panel display and solar cells. In particular, amorphous Ga-In-Zn-O (a-GIZO) thin films are promising channel materials for thin film transistors (TFTs) because a-GIZO TFTs exhibit large field-effect mobility (>10 cm2/V s) irrespective of their fabrication on various substrates, such as silicon, glass, plastic, polyimide, polyethylene terephthalate (PET), cellulose paper and flexible substrates. In addition, they have superior uniformity, low processing temperature, possibility of large-area deposition and long term stability, and moreover they are cost effective.
In recent years, a large progress has been made in high performance TFTs based on a-GIZO as channel layers. Amorphous semiconductors have defect states originating from structural disorder and defect, which strongly affect carrier transport properties and devices performances. However, fundamental material properties of a-GIZO such as the band alignment and defect states, which are important for devices structure and circuit configuration have not been investigated in detail so far. Moreover, any investigation of band alignment and defect states of a-GIZO thin films is very important to understand the transport mechanism and to improve device performances.
In this study, we have investigated the band gap, valence band offset and defect states of GIZO thin films by using reflection electron energy loss spectroscopy (REELS), X-ray photoelectron spectroscopy (XPS), thermally stimulated exo-electron emission (TSEE) and photoinduced current transient spectroscopy (PICT). The band gap and valence band offset (VBO or △EV) allow us to determine the conduction band offset △EC) by using the relation: △EC = Eg(SiO2) - △EV (GIZO/SiO2/Si) - Eg(a-GIZO). The band gap is 3.2eV, and the conduction band offset of GIZO is 3.62 eV. The shallow defect states obtained via PICT were at 0.24eV and 0.53eV below the conduction band minimum of a-GIZO thin film, and the deep defect state obtained by means of TSEE is 1.827eV below the conduction band minimum of GIZO thin film.