Wostatek T, Tian L, Wei Y, Neumeier S, Schimmel S (2026)
Publication Language: English
Publication Type: Conference contribution, Abstract of a poster
Publication year: 2026
City/Town: Berlin
Pages Range: 38
Conference Proceedings Title: Abstract Book 9th International Workshop on Crystal Growth Technology
Event location: Berlin
URI: https://iwcgt-9.ikz-berlin.de/ img/2vm89F8/ iwcgt-9-abstractbook.pdf
Nitride semiconductors get increasingly relevant to optoelectronics and power electronics, especially gallium nitride (GaN).1-3 Vertical high-power transistors and diodes contribute to the driving force to develop bulk crystals of GaN in high structural quality with a high free carrier concentration.2 The ammonothermal method has emerged as a key technique for the growth of GaN single crystals with a high structural quality.2,4 Major remaining challenges for the ammonothermal method are high concentrations of point defects, which limit the achievable free carrier concentrations of ammonothermal GaN.2,4 Oxygen is the most significant, insufficiently controlled impurity in ammonothermal GaN, dominating its free carrier mobility.4,5 One method to address this issue is to getter oxygen in or directly before the growth process.
This contribution reports the development of a concept for identifying prospective getter materials and an experimental method for investigating the potential of materials as oxygen getters for the growth of nitrides, especially GaN, in the ammonothermal process. The concept is based on a comparative analysis of vapor pressure curves of the most stable nitrides, oxynitrides and oxides and validated with literature data of ammonothermal crystal growth experiments. The experimental method, which can be applied for investigation of the gettering capacity of inner surfaces of reactors as well as sample materials inside the reactor, involves a step-wise thermal treatment (21 ± 1 h) in a closed system containing residual oxygen in an argon atmosphere. Subsequently, the oxygen concentration in the gas sampled from the reactor is analyzed using a potentiometric oxygen sensor.
First results demonstrate the oxygen gettering effect of nickel-based superalloys, as typical structural materials for ammonothermal reactors (autoclaves). In this context, new and unused Inconel® 718 and Haynes® 282 autoclaves as well as one used Inconel® 718 autoclave, which had repeatedly been used for ammonothermal experiments, were analyzed. The oxygen gettering effect of nickel-based superalloys can be ascribed to the alloying element chromium (Cr) by the formation of chromium oxide, which also rationalizes the developed concept.
References:
[1] H. Amano et al., J. Phys. D: Appl. Phys. 53, 503001, 2020.
[2] R. Kucharski at al., J. Appl. Phys. 128, 050902, 2020.
[3] B. N. Pushpakaran et al., J. elec. Mat. 49, S. 6247-6262, 2020.
[4] T. Wostatek et al., Materials 17, 3104, 2024.
[5] W. Jiang et al., Appl. Phys. Express 10, 075506, 2017.
APA:
Wostatek, T., Tian, L., Wei, Y., Neumeier, S., & Schimmel, S. (2026, June). Experimental method and thermodynamic concept for investigating and rationalizing oxygen gettering by ammonothermal reactor walls. Poster presentation at 9th International Workshop on Crystal Growth Technology, Berlin.
MLA:
Wostatek, Thomas, et al. "Experimental method and thermodynamic concept for investigating and rationalizing oxygen gettering by ammonothermal reactor walls." Presented at 9th International Workshop on Crystal Growth Technology, Berlin Berlin, 2026.
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