Investigation of defects in In–Ga–Zn oxide thin film using electron spin resonance signals

In–Ga–Zn oxide (IGZO) is a next-generation semiconductor material seen as an alternative to silicon. Despite the importance of the controllability of characteristics and the reliability of devices, defects in IGZO have not been fully understood. We investigated defects in IGZO thin films using elect...

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Bibliographic Details
Published in:Journal of applied physics 2014-04, Vol.115 (16)
Main Authors: Nonaka, Yusuke, Kurosawa, Yoichi, Komatsu, Yoshihiro, Ishihara, Noritaka, Oota, Masashi, Nakashima, Motoki, Hirohashi, Takuya, Takahashi, Masahiro, Yamazaki, Shunpei, Obonai, Toshimitsu, Hosaka, Yasuharu, Koezuka, Junichi, Yamauchi, Jun
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
ANNEALING
Applied physics
CONCENTRATION RATIO
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Conduction electrons
Controllability
Defects
Electron paramagnetic resonance
Electron spin
ELECTRON SPIN RESONANCE
ELECTRONS
First principles
G VALUE
GALLIUM COMPOUNDS
Heat treatment
Hydrogen atoms
INDIUM COMPOUNDS
Indium gallium zinc oxide
Oxygen
SEMICONDUCTOR MATERIALS
Spin resonance
TEMPERATURE DEPENDENCE
THIN FILMS
VACANCIES
ZINC OXIDES
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Summary:In–Ga–Zn oxide (IGZO) is a next-generation semiconductor material seen as an alternative to silicon. Despite the importance of the controllability of characteristics and the reliability of devices, defects in IGZO have not been fully understood. We investigated defects in IGZO thin films using electron spin resonance (ESR) spectroscopy. In as-sputtered IGZO thin films, we observed an ESR signal which had a g-value of g = 2.010, and the signal was found to disappear under thermal treatment. Annealing in a reductive atmosphere, such as N2 atmosphere, generated an ESR signal with g = 1.932 in IGZO thin films. The temperature dependence of the latter signal suggests that the signal is induced by delocalized unpaired electrons (i.e., conduction electrons). In fact, a comparison between the conductivity and ESR signal intensity revealed that the signal's intensity is related to the number of conduction electrons in the IGZO thin film. The signal's intensity did not increase with oxygen vacancy alone but also with increases in both oxygen vacancy and hydrogen concentration. In addition, first-principle calculation suggests that the conduction electrons in IGZO may be generated by defects that occur when hydrogen atoms are inserted into oxygen vacancies.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4873638