From Amorphous to β-Gallium Oxide: Practical Implementation of Energetics Considerations in Process Design and Optimization
Bibliographic record
Abstract
Gallium oxide (Ga 2 O 3 ) is a wide bandgap material (bandgap ~4.0 eV – 5.2 eV) with a large breakdown field that has considerably high figures of merit (FOM) in power handling compared to other wide bandgap semiconductor materials in use today (such as GaN and SiC) [1, 2]. Gallium oxide is also expected to expand the operating spectral range of optoelectronic devices to deep UV. Properties of gallium oxide depend on its crystal structure; amorphous [3, 4] as well as different crystalline forms [5] of this material have been used in electronic and optoelectronic devices. Among gallium oxide crystalline polymorphs, β-Ga 2 O 3 has attracted the most attention because it is the most stable gallium oxide polymorph and, therefore, can ultimately be obtained by heating other gallium oxide polymorphs (and even amorphous gallium oxide) at sufficiently high temperatures (ca. 550°C and above); this polymorph can also be obtained from the melt at high temperatures (ca. 1800°C) using bulk crystal growth techniques [1, 6]. In the thin film form, growing high quality β-Ga 2 O 3 is only possible on very limited substrates (e.g., β-Ga 2 O 3 native substrate and sapphire) while having to carefully choose very specific process conditions based on each process and the instrument being used. In this work, we present strategies and guidelines, based on energetics considerations, that make it possible to design epitaxial deposition processes that achieve β-Ga 2 O 3 thin films at low temperatures (< 300°C). We use the atomic layer deposition (ALD) technique to achieve dense and pinhole-free films of amorphous gallium oxide. Then, we revise the deposition process conditions step-by-step so that the energetics of the process can lead us to obtain high quality epitaxial β-Ga 2 O 3 at low temperatures while not being limited to β-Ga 2 O 3 native substrates or very specific (or instrument-dependent) process conditions. The results presented in this work facilitate the implementation of Ga 2 O 3 in next generation wide bandgap electronic devices. References: [1] Pearton, S. J.; Yang, J.; Cary, P. H.; Ren, F.; Kim, J.; Tadjer, M. J.; Mastro, M. A. A Review of Ga2O3 Materials, Processing, and Devices. Appl. Phys. Rev. 2018 , 5 , 011301. [2] Rafie Borujeny, E.; Sendetskyi, O.; Fleischauer, M. D.; Cadien, K. C. Low Thermal Budget Heteroepitaxial Gallium Oxide Thin Films Enabled by Atomic Layer Deposition. ACS Appl. Mater. Interfaces 2020 , 12 , 44225-44237. [3] Kim, J.; Sekiya, T.; Miyokawa, N.; Watanabe, N.; Kimoto, K.; Ide, K.; Toda, Y.; Ueda, S.; Ohashi, N.; Hiramatsu, H.; Hosono, H.; Kamiya, T. Conversion of an Ultra-Wide Bandgap Amorphous Oxide Insulator to a Semiconductor. NPG Asia Mater. 2017 , 9 , e359. [4] Xiao, S.; Deng, Y.; Chen, Z.; Wang, Y.; Yu, J.; Tang, W.; Wu, Z. Flexible and Highly Stable Solar-Blind Photodetector Based on Room-Temperature Synthesis of Amorphous Ga2O3 Film. J. Phys. D: Appl. Phys. 2020 , 53 , 484004. [5] Ahmadi, E.; Oshima, Y. Materials Issues and Devices of α- and β-Ga2O3. J. Appl. Phys. 2019 , 126 , 160901. [6] Mastro, M. A.; Kuramata, A.; Calkins, J.; Kim, J.; Ren, F.; Pearton, S. J. Perspective—Opportunities and Future Directions for Ga2O3. ECS J. Solid State Sci. Technol. 2017 , 6 , P356-P359.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".