Gallium oxide (Ga2O3) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) applying a capacitively coupled plasma source where trimethylgallium (TMGa) as the gallium precursor and oxygen (O2) plasma were used in a substrate temperature (Ts) in range of 80–200 °C. TMGa exhibits high vapor pressure and therefore facilitates deposition at lower substrate temperatures. The Ga2O3 films were characterized by spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), and capacitance-voltage (C-V) measurements. The SE data show linear thickness evolution with a growth rate of ∼0.66 Å per cycle and inhomogeneity of ≤2% for all samples. The refractive index of the Ga2O3 thin films is 1.86 ± 0.01 (at 632.8 nm) and independent of temperature, whereas the bandgap slightly decreases from 4.68 eV at Ts of 80 °C to 4.57 eV at 200 °C. XPS analysis revealed ideal stoichiometric gallium to oxygen ratios of 2:3 for the Ga2O3 layers with the lowest carbon contribution of ∼10% for the sample prepared at 150 °C. The permittivity of the layers is 9.7 ± 0.2 (at 10 kHz). In addition, fixed and mobile oxide charge densities of 2–4 × 1012 and 1–2 × 1012 cm−2, respectively, were observed in the C-V characteristics. Moreover, the Ga2O3 films show breakdown fields in the range of 2.2–2.7 MV/cm. Excellent optical and electrical material properties are maintained even at low substrate temperatures as low as 80 °C. Hence, the TMGa/O2 PEALD process is suitable for electronic and optoelectronic applications where low-temperature growth is required.
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Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition
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March 2020
Research Article|
January 14 2020
Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition
Special Collection:
Special Topic Collection on Atomic Layer Deposition (ALD)
Ali Mahmoodinezhad
;
Ali Mahmoodinezhad
1
Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Zuse-Str. 1, 03046 Cottbus, Germany
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Christoph Janowitz
;
Christoph Janowitz
1
Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Zuse-Str. 1, 03046 Cottbus, Germany
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Franziska Naumann
;
Franziska Naumann
2
SENTECH Instruments GmbH
, Schwarzschildstraße 2, 12489 Berlin, Germany
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Paul Plate
;
Paul Plate
2
SENTECH Instruments GmbH
, Schwarzschildstraße 2, 12489 Berlin, Germany
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Hassan Gargouri;
Hassan Gargouri
2
SENTECH Instruments GmbH
, Schwarzschildstraße 2, 12489 Berlin, Germany
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Karsten Henkel
;
Karsten Henkel
a)
1
Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Zuse-Str. 1, 03046 Cottbus, Germany
3
Applied Physics and Sensor Technology, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany
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Dieter Schmeißer
;
Dieter Schmeißer
3
Applied Physics and Sensor Technology, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany
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Jan Ingo Flege
Jan Ingo Flege
1
Applied Physics and Semiconductor Spectroscopy, Brandenburg University of Technology Cottbus–Senftenberg
, K.-Zuse-Str. 1, 03046 Cottbus, Germany
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a)
Electronic mail: henkel@b-tu.de
Note: This paper is part of the 2020 Special Topic Collection on Atomic Layer Deposition (ALD).
J. Vac. Sci. Technol. A 38, 022404 (2020)
Article history
Received:
November 01 2019
Accepted:
December 20 2019
Citation
Ali Mahmoodinezhad, Christoph Janowitz, Franziska Naumann, Paul Plate, Hassan Gargouri, Karsten Henkel, Dieter Schmeißer, Jan Ingo Flege; Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition. J. Vac. Sci. Technol. A 1 March 2020; 38 (2): 022404. https://doi.org/10.1116/1.5134800
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