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Evaluation of Sub-Gap States in Amorphous In-Ga-Zn-O Thin Films Treated with Various Process Conditions

Published online by Cambridge University Press:  13 February 2014

Kazushi Hayashi ,
Aya Hino ,
Hiroaki Tao ,
Yasuyuki Takanashi ,
Shinya Morita ,
Hiroshi Goto  and
Toshihiro Kugimiya
Kazushi Hayashi
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Aya Hino
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Hiroaki Tao
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Yasuyuki Takanashi
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Shinya Morita
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Hiroshi Goto
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
Toshihiro Kugimiya
Affiliation:
Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5 Takatsuka-dai, Nishi-ku, Kobe, 651-2271, Japan.
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Abstract

In the present study, the sub-gap states of amorphous In-Ga-Zn-O (a-IGZO) thin films treated with various process conditions have been evaluated by means of capacitance-voltage (C-V) characteristics and isothermal capacitance transient spectroscopy (ICTS). It was found that the space-charge densities of the a-IGZO decreased as the oxygen partial pressure was increased during the sputtering of a-IGZO thin films. The ICTS spectra for the 4, 8, and 12 % samples were similar and the peak positions were found to be around 1 × 10-2 s at 180 K. On the other hand, the peak position for the 20 % sample shifted to a longer time regime and was located at around 2 × 10-1 s at 180 K. The total densities of the traps for the 4, 8, and 12 % samples were calculated to be 5−6 × 1016 cm-3, while that for 20 % was one order of magnitude lower than the others. From Thermal desorption spectrometer, it was found that desorption of Zn atoms started at a temperature higher than 300 °C for the 4 % sample, while desorption of Zn was not observed for the 20 % sample. The introduction of the sub-gap states could be attributed to oxygen-rich and/or Zn-deficient defects in the a-IGZO thin films formed during thermal annealing.

Keywords

semiconductingdefectselectrical properties
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1633: Symposium R – Oxide Semiconductors , 2014 , pp. 55 - 60
Copyright
Copyright © Materials Research Society 2014 

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References

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