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. 2022 Jan 3;15(1):334.
doi: 10.3390/ma15010334.

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Rostislav Velichko  1 , Yusaku Magari  2 , Mamoru Furuta  1   3   4
Affiliations

Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Rostislav Velichko et al. Materials (Basel). .

Abstract

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

Keywords: defect passivation; flexible electronics; hydrogen in In–Ga–Zn–O; low-temperature activation; oxide semiconductors; oxygen diffusion.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure A1
Figure A1
Annealing time dependence of the carrier density for H-doped IGZO films after 1 h annealing in N2 at 150 °C.
Figure 1
Figure 1
Properties of conventional IGZO film: (a) carrier density obtained during the in situ Hall measurement in air and vacuum; (b) O 1s spectra before and after 1 h annealing in air at 300 °C; (c) electronic structure around the band gap region for as-deposited and after annealing at various temperature.
Figure 2
Figure 2
Carrier density of H doped IGZO films obtained from the in situ Hall measurement performed in air and vacuum atmosphere: (a) R[H2] = 2%; (b) R[H2] = 5%; (c) R[H2] = 8%; (d) Carrier density variation as a function of annealing time at fixed temperature of 150 °C performed in air.
Figure 3
Figure 3
O 1s spectra of IGZO and IGZO:H films: (a) and (c) as-deposited before and after deconvolution, respectively; (b) and (d) annealed films in air for 1 h before and after deconvolution, respectively.
Figure 4
Figure 4
HAXPES spectra around band gap of the IGZO films deposited at different R[H2] and at fixed R[O2] = 1%: (a) as-deposited; (b) before and after annealing for 1 h in air at different temperature.
Figure 5
Figure 5
XRR results of the IGZO films deposited at different R[H2] and at fix R[O2] of 1%: (a) as-deposited; (b) after annealing in air for 1 h at the annealing temperature of 150 °C. The insets show the reflectivity intensity near the critical angle representing the change in film density upon the hydrogen incorporation.
See this image and copyright information in PMC

References

    1. Hosono H., Yasakawa M., Kawazone H. Novel oxide amorphous semiconductors: Transparent conducting amorphous oxides. J. Non Cryst. Solids. 1996;203:334–344. doi: 10.1016/0022-3093(96)00367-5. - DOI
    1. Nomura K., Ohta H., Takagi A., Kamiya T., Hirano M., Hosono H. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors. Nature. 2004;432:488–492. doi: 10.1038/nature03090. - DOI - PubMed
    1. Kim J., Bang J., Nakamura N., Hosono H. Ultra-wide bandgap amorphous oxide semiconductors for NBIS-free thin-film transistors. APL Mater. 2019;7:022501. doi: 10.1063/1.5053762. - DOI
    1. Shiah Y.-S., Sim K., Ueda S., Kim J., Hosono H. Unintended Carbon-Related Impurity and Negative Bias Instability in High-Mobility Oxide TFTs. IEEE Electron Device Lett. 2021;42:1319–1322. doi: 10.1109/LED.2021.3101654. - DOI
    1. Fortunato E., Barquinha P., Martins R. Oxide Semiconductor Thin-Film Transistors: A Review of Recent Advances. Adv. Mater. 2012;24:2945–2986. doi: 10.1002/adma.201103228. - DOI - PubMed