Relationship between non-localized tail states and carrier transport in amorphous oxide semiconductor, In-Ga-Zn-O

• Published in: Physica status solidi. A, Applications and materials science Vol. 205; no. 8; pp. 1910 - 1914
• Main Authors: Nomura, K., Kamiya, T., Ohta, H., Shimizu, K., Hirano, M., Hosono, H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.08.2008; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: 68.55.−a; 71.55.Jv; 73.61.Jc; 81.40.Ef; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Disordered solids; Electronic transport in condensed matter; Exact sciences and technology; Physics; Hall mobility; Amorphous semiconductors; Electron mobility; Oxides; Carrier mobility; Thermal annealing; Carrier density; Transparent material; Structure relaxation
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.200778936

The relationship between non‐localized tail states and carrier transport in transparent amorphous oxide semiconductor, In–Ga–Zn–O (a‐IGZO), was investigated. It was found that the energy width (E0) of the non‐localized tail states varied from <7 meV to 20 meV depending on the film deposition conditions (i.e. film quality). At carrier concentrations of ∼1019 cm–3, Hall mobilities larger than 10 cm2 (V s)–1 were obtained for the high‐quality films, while they were only several cm2 (V s)–1 for low‐quality films that have large E0 values ∼20 meV. However, even for low‐quality films, the E0 value decreased from 20 meV to 7 meV and their Hall mobilities were increased from ∼1 cm2 to >10 cm2 (V s)–1 by post thermal annealing at ≥300 °C. These observations indicate that structural relaxation associated with electron transport starts from ∼300 °C, which is much lower than the crystallization temperature (∼520 °C). This situation is similar to the case of amorphous metals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)