Thermal Conductivity of Amorphous Indium--Gallium--Zinc Oxide Thin Films

We investigated the thermal conductivity of 200-nm-thick amorphous indium--gallium--zinc-oxide (a-IGZO) films. Films with a chemical composition of $\text{In}:\text{Ga}:\text{Zn}= 1:1:0.6$ were prepared by dc magnetron sputtering using an IGZO ceramic target and an Ar--O 2 sputtering gas. The carrie...

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Published inApplied physics express Vol. 6; no. 2; pp. 021101 - 021101-3
Main Authors Yoshikawa, Toru, Yagi, Takashi, Oka, Nobuto, Jia, Junjun, Yamashita, Yuichiro, Hattori, Koichiro, Seino, Yutaka, Taketoshi, Naoyuki, Baba, Tetsuya, Shigesato, Yuzo
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.02.2013
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Summary:We investigated the thermal conductivity of 200-nm-thick amorphous indium--gallium--zinc-oxide (a-IGZO) films. Films with a chemical composition of $\text{In}:\text{Ga}:\text{Zn}= 1:1:0.6$ were prepared by dc magnetron sputtering using an IGZO ceramic target and an Ar--O 2 sputtering gas. The carrier density of the films was systematically controlled from $10^{14}$ to ${>}10^{19}$ cm -3 by varying the O 2 flow ratio. Their Hall mobility was slightly higher than 10 cm 2 $\cdot$V -1 $\cdot$s -1 . Those films were sandwiched between 100-nm-thick Mo layers; their thermal diffusivity, measured by a pulsed light heating thermoreflectance technique, was ${\sim}5.4\times 10^{-7}$ m 2 $\cdot$s -1 and was almost independent of the carrier density. The average thermal conductivity was 1.4 W$\cdot$m -1 $\cdot$K -1 .
Bibliography:Carrier density ($n$), Hall mobility ($\mu$) and resistivity ($\rho$) of a-IGZO films as functions of O 2 flow ratio during deposition. The applied magnetic field for the Hall measurement was changed from the dc method to the ac method when the resistivity exceeded 1 $\Omega$$\cdot$cm. Normalized transient temperatures of Mo/a-IGZO/Mo three-layered films, where the a-IGZO was deposited at the O 2 flow ratios of 0 and 2%, obtained by the pulsed light heating thermoreflectance technique. Thermal conductivities of a-IGZO and a-IZO films as a function of carrier density. A red dashed curve represents estimated thermal conductivity of a-IGZO film derived from sum of the contributions of phonons ($\lambda_{\text{ph}}$) and electrons ($\lambda_{\text{el}}$). $\lambda_{\text{el}}$ is calculated using Wiedemann--Franz law, where Lorenz number and Hall mobility are $2.45\times 10^{-8}$ W$\cdot$$\Omega$$\cdot$K -2 and 10.9 cm 2 $\cdot$V -1 $\cdot$s -1 , respectively. A blue dashed line shows $\lambda_{\text{ph}}$ of the IGZO films. Young's moduli of a-IGZO films with thicknesses of 200 and 1000 nm as a function of indentation depth.
ISSN:1882-0778
1882-0786
DOI:10.7567/APEX.6.021101