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- Khartsev, Sergey, et al.
(författare)
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High‐Quality Si‐Doped β‐Ga 2 O 3 Films on Sapphire Fabricated by Pulsed Laser Deposition
- 2020
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 258:2, s. 2000362-2000362
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Tidskriftsartikel (refereegranskat)abstract
- Pulsed laser ablation is used to form high-quality silicon-doped β-Ga2O3 films on sapphire by alternatively depositing Ga2O3 and Si from two separate sources. X-ray analysis reveals a single crystallinity with a full width at half maximum for the rocking curve around the (−201) reflection peak of 1.6°. Silicon doping concentration is determined by elastic recoil detection analysis (ERDA), and the best electrical performance is reached at a Si concentration of about 1 × 1020 cm−3, using optimized deposition parameters. It is found that a high crystalline quality and a mobility of about 2.9 cm2 (V s)−1 can be achieved by depositing Si and Ga2O3 from two separate sources. Two types of Schottky contacts are fabricated: one with a pure Pt and one with a PtOx composition. Electrical results from these structures are also presented.
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| 2. |
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| 3. |
- Zubkins, Martins, et al.
(författare)
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Amorphous p-Type Conducting Zn–xIr Oxide (x > 0.13) Thin Films Deposited by Reactive Magnetron Cosputtering
- 2022
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Ingår i: Physica status solidi. B, Basic research. - : John Wiley and Sons Inc. - 0370-1972 .- 1521-3951. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- Zinc–iridium oxide (Zn–Ir–O) thin films have been demonstrated as a p-type conducting material. However, the stability of p-type conductivity with respect to chemical composition or temperature is still unclear. In this study we discuss the local atomic structure and the electrical properties of Zn–Ir–O films in the large Ir concentration range. The films are deposited by reactive DC magnetron co-sputtering at two different substrate temperatures—without intentional heating and at 300 °C. Extended X-ray absorption fine structure (EXAFS) analysis reveals that strongly disordered ZnO4 tetrahedra are the main Zn complexes in Zn–Ir–O films with up to 67.4 at% Ir. As the Ir concentration increases, an effective increase of Ir oxidation state is observed. Reverse Monte Carlo analysis of EXAFS at Zn K-edge shows that the average Zn–O interatomic distance and disorder factor increase with the Ir concentration. We observed that the nano-crystalline w-ZnO structure is preserved in a wider Ir concentration range if the substrate is heated during deposition. At low Ir concentration, the transition from n- to p-type conductivity is observed regardless of the temperature of the substrates. Electrical resistivity decreases exponentially with the Ir concentration in the Zn–Ir–O films.
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| 4. |
- Zubkins, Martins, et al.
(författare)
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Deposition of Ga2O3 thin films by liquid metal target sputtering
- 2023
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 209, s. 111789-
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on the deposition of amorphous and crystalline thin films of Ga2O3 by reactive pulsed direct current magnetron sputtering from a liquid gallium target onto fused (f-) quartz and c plane (c-) sapphire sub-strates, where the temperature of the substrate is varied from room temperature (RT) to 800 degrees C. The deposition rate (up to 37 nm/min at RT on f-quartz and 5 nm/min at 800 degrees C on c-sapphire) is two to five times higher than the data given in the literature for radio frequency sputtering. Deposited onto unheated substrates, the films are X-ray amorphous. Well-defined X-ray diffraction peaks of 13-Ga2O3 start to appear at a substrate temperature of 500 degrees C. Films grown on c-sapphire at temperatures above 600 degrees C are epitaxial. However, the high rocking curve full width at half maximum values of X2.4-2.5 degrees are indicative of the presence of defects. A dense and void-free microstructure is observed in electron microscopy images. Composition analysis show stoichiometry close to Ga2O3 and no traces of impurities. The optical properties of low absorptance (<1%) in the visible range and an optical band gap of approximately 5 eV are consistent with the data in the literature for Ga2O3 films produced by other deposition methods.
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