European Journal of Inorganic Chemistry

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Editor: Karen Hindson, Deputy Editor: Preeti Vashi

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Online ISSN: 1099-0682

Associated Title(s): Angewandte Chemie International Edition, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemCatChem, Zeitschrift für anorganische und allgemeine Chemie

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Press Release

European Journal of Inorganic Chemistry , 2013, 5387–5399
doi: 10.1002/ejic.201300958

Nr. 02/2013
November 5, 2013

Growing Gallium Nitride Crystals

Understanding the ammonothermal method for growing GaN crystals

Contact: Rainer Niewa, Universität Stuttgart (Germany)
Registered journalists may download the original article here:
Intermediates in Ammonothermal GaN Crystal Growth under Ammonoacidic Conditions

Gallium nitride (GaN) is an important material for the semiconductor industry. It features a wide band gap and high thermal conductivity at room temperature, which make it a good material for optoelectronic devices and high-performance radio-frequency microdevices. In the European Journal of Inorganic Chemistry, Rainer Niewa and co-workers at the University of Stuttgart and Ludwig Maximilians University of Munich, Germany, report the existence of ammoniates of gallium halides in the ammonothermal growth of GaN and provide a rigorous characterization of these compounds.

Growing Gallium Nitride Crystals - Understanding the ammonothermal method for growing GaN crystals
© Wiley-VCH

High-quality GaN single crystals are difficult to obtain. The ammonothermal growth technology, which is analogous to the hydrothermal method but uses supercritical ammonia instead of water, is a promising method to grow the best quality GaN crystals. To obtain soluble Ga species, typically ammonium halides or alkali metal amides are added to the reaction mixture. However, the chemistry involved in the crystal growth process is not well understood. Rainer Niewa et al. provide the first comprehensive information on the gallium-containing ionic species likely to predominate in the reaction mixtures used to prepare GaN by using ammonium halides as additive. They elucidate the crystal structures of ammoniates of gallium halides that are highly soluble in supercritical ammonia.

Knowing the solid-state structures of these species, the number of coordinated ammonia and halide ligands, and the conditions under which these compounds form and decompose is a great aid in predicting the mechanisms of the ammonothermal growth of GaN crystals.

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About the Author

Professor Rainer Niewa works in the Institute of Inorganic Chemistry at the University of Stuttgart, Germany. His research involves inorganic solid-state chemistry and development of new materials. The work largely focuses on the synthesis and detailed characterization of innovative materials with special focus on metal nitrides.