Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions
With the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are stu...
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| author | Saskia Schimmel Daisuke Tomida Tohru Ishiguro Yoshio Honda Shigefusa F. Chichibu Hiroshi Amano |
| author_facet | Saskia Schimmel Daisuke Tomida Tohru Ishiguro Yoshio Honda Shigefusa F. Chichibu Hiroshi Amano |
| author_sort | Saskia Schimmel |
| collection | DOAJ |
| description | With the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are studied using a 2D axis symmetrical numerical model. In addition, experimental crystal growth results are analyzed in terms of etch-back and crystal growth rates as a function of vertical seed position. The numerical results of internal process conditions are discussed. Variations along the vertical axis of the autoclave are analyzed using both numerical and experimental data. During the transition from quasi-stable conditions of the dissolution stage (etch-back process) to quasi-stable conditions of the growth stage, significant temperature differences of 20 K to 70 K (depending on vertical position) occur temporarily between the crystals and the surrounding fluid. These lead to maximum rates of seed temperature change of 2.5 K/min to 1.2 K/min depending on vertical position. Based on temperature differences between seeds, fluid, and autoclave wall upon the end of the set temperature inversion process, deposition of GaN is expected to be favored on the bottom seed. The temporarily observed differences between the mean temperature of each crystal and its fluid surrounding diminish about 2 h after reaching constant set temperatures imposed at the outer autoclave wall, whereas approximately quasi-stable conditions are reached about 3 h after reaching constant set temperatures. Short-term fluctuations in temperature are mostly due to fluctuations in velocity magnitude, usually with only minor variations in the flow direction. |
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| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-11T07:18:37Z |
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| spelling | doaj.art-7849afc2f112463681c8b4cea913737e2023-11-17T08:06:01ZengMDPI AGMaterials1996-19442023-02-01165201610.3390/ma16052016Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage ConditionsSaskia Schimmel0Daisuke Tomida1Tohru Ishiguro2Yoshio Honda3Shigefusa F. Chichibu4Hiroshi Amano5Crystal Growth Lab, Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyInstitute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, JapanInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, JapanInstitute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, JapanInstitute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, JapanInstitute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, JapanWith the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are studied using a 2D axis symmetrical numerical model. In addition, experimental crystal growth results are analyzed in terms of etch-back and crystal growth rates as a function of vertical seed position. The numerical results of internal process conditions are discussed. Variations along the vertical axis of the autoclave are analyzed using both numerical and experimental data. During the transition from quasi-stable conditions of the dissolution stage (etch-back process) to quasi-stable conditions of the growth stage, significant temperature differences of 20 K to 70 K (depending on vertical position) occur temporarily between the crystals and the surrounding fluid. These lead to maximum rates of seed temperature change of 2.5 K/min to 1.2 K/min depending on vertical position. Based on temperature differences between seeds, fluid, and autoclave wall upon the end of the set temperature inversion process, deposition of GaN is expected to be favored on the bottom seed. The temporarily observed differences between the mean temperature of each crystal and its fluid surrounding diminish about 2 h after reaching constant set temperatures imposed at the outer autoclave wall, whereas approximately quasi-stable conditions are reached about 3 h after reaching constant set temperatures. Short-term fluctuations in temperature are mostly due to fluctuations in velocity magnitude, usually with only minor variations in the flow direction.https://www.mdpi.com/1996-1944/16/5/2016ammonothermalgallium nitridecrystal growthnumerical simulationcomputational fluid dynamicsnatural convection |
| spellingShingle | Saskia Schimmel Daisuke Tomida Tohru Ishiguro Yoshio Honda Shigefusa F. Chichibu Hiroshi Amano Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions Materials ammonothermal gallium nitride crystal growth numerical simulation computational fluid dynamics natural convection |
| title | Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions |
| title_full | Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions |
| title_fullStr | Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions |
| title_full_unstemmed | Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions |
| title_short | Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions |
| title_sort | temperature field flow field and temporal fluctuations thereof in ammonothermal growth of bulk gan transition from dissolution stage to growth stage conditions |
| topic | ammonothermal gallium nitride crystal growth numerical simulation computational fluid dynamics natural convection |
| url | https://www.mdpi.com/1996-1944/16/5/2016 |
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