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Subgap states, doping and defect formation energies in amorphous oxide semiconductor a‐InGaZnO 4 studied by density functional theory
Author(s) -
Kamiya Toshio,
Nomura Kenji,
Hosono Hideo
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200983772
Subject(s) - density functional theory , doping , materials science , amorphous solid , valence (chemistry) , hydrogen , density of states , oxide , semiconductor , oxygen , chemical physics , atomic physics , computational chemistry , crystallography , chemistry , condensed matter physics , optoelectronics , physics , organic chemistry , metallurgy
Amorphous In‐Ga‐Zn‐O (a‐IGZO) is expected for channel layers in thin‐film transistors (TFTs). It is known that a‐IGZO is sensitive to an O/H‐containing atmosphere; therefore, it is important to clarify the roles of oxygen and hydrogen in a‐IGZO. This paper provides atomic and electronic structures, formation energies of defects and bond energies in a‐IGZO calculated by first‐principles density functional theory (DFT). It was confirmed that oxygen deficiencies having small formation energies (2–3.6 eV) form either deep fully‐occupied localized states near the valence band maximum or donor states, which depend on their local structures. All the hydrogen doping form OH bond and work as a donor. The stable OH bonds have small formation energy of ∼0.45 eV and consist of three metal cations coordinated to the O ion. The bond energy of GaO is calculated to be ∼2.0 eV, which is the largest among the chemical bonds in a‐IGZO (1.7 eV for InO and 1.5 eV for ZnO). This result supports the idea that the incorporation of Ga stabilizes a‐IGZO TFTs.