Editing Gallium nitride (section)

== Synthesis ==
=== Bulk substrates ===
GaN crystals can be grown from a molten Na/Ga melt held under 100 atmospheres of pressure of N<sub>2</sub> at 750&nbsp;°C. As Ga will not react with N<sub>2</sub> below 1000&nbsp;°C, the powder must be made from something more reactive, usually in one of the following ways:
: 2 Ga + 2 NH<sub>3</sub> → 2 GaN + 3 H<sub>2</sub><ref>{{cite book | title=Ceramics Science and Technology, Volume 2: Materials and Properties | isbn=978-3527802579 | author=Ralf Riedel, I-Wei Chen| date=2015 | publisher=Wiley-Vch}}</ref>
: Ga<sub>2</sub>O<sub>3</sub> + 2 NH<sub>3</sub> → 2 GaN + 3 H<sub>2</sub>O<ref>{{cite book | title=Nitride Semiconductor Light-Emitting Diodes (LEDs) | isbn=978-0857099303 | author=Jian-Jang Huang, Hao-Chung Kuo, Shyh-Chiang Shen |pages=68 | date= 2014| publisher=Woodhead }}</ref>

Gallium nitride can also be synthesized by injecting ammonia gas into molten gallium at {{val|900|-|980|u=°C}} at normal atmospheric pressure.<ref>{{cite journal | title=Synthesis of gallium nitride by ammonia injection into gallium melt | author=M. Shibata, T. Furuya, H. Sakaguchi, S. Kuma | doi=10.1016/S0022-0248(98)00819-7 | journal=Journal of Crystal Growth | volume=196 | issue=1 | pages=47–52| date=1999| bibcode=1999JCrGr.196...47S}}</ref>

=== Metal-organic vapour phase epitaxy ===
Blue, white and ultraviolet [[Light-emitting diode|LED]]s are grown on industrial scale by [[Metalorganic vapour-phase epitaxy|metalorganic vapour-phase epitaxy (MOVPE)]].<ref>{{Cite patent|number=US8357945B2|title=Gallium nitride crystal and method of making same|gdate=2013-01-22|invent1=D'Evelyn|invent2=Park|invent3=LeBoeuf|invent4=Rowland|inventor1-first=Mark Philip|inventor2-first=Dong-Sil|inventor3-first=Steven Francis|inventor4-first=Larry Burton|url=https://patents.google.com/patent/US8357945B2/en}}</ref><ref>{{Cite web |title=Google Patents |url=https://patents.google.com/?q=gallium+nitride&assignee=cornell |access-date=2022-10-20 |website=patents.google.com}}</ref> The precursors are [[ammonia]] with either [[trimethylgallium]] or [[triethylgallium]], the carrier gas being [[nitrogen]] or [[hydrogen]]. Growth temperature ranges between {{val|800|and|1100|u=°C}}. Introduction of [[trimethylaluminium]] and/or [[trimethylindium]] is necessary for growing quantum wells and other kinds of [[heterostructure]]s.

=== Molecular beam epitaxy ===
Commercially, GaN crystals can be grown using [[molecular beam epitaxy]] or MBE. This process can be further modified to reduce dislocation densities.  First, an ion beam is applied to the growth surface in order to create nanoscale roughness.  Then, the surface is polished. This process takes place in a vacuum. Polishing methods typically employ a liquid electrolyte and UV irradiation to enable mechanical removal of a thin oxide layer from the wafer. More recent methods have been developed that utilize solid-state [[polymer electrolytes]] that are solvent-free and require no radiation before polishing.<ref>{{Cite journal|date=2018-12-01|title=Liquid electrolyte-free electrochemical oxidation of GaN surface using a solid polymer electrolyte toward electrochemical mechanical polishing|journal=Electrochemistry Communications|language=en|volume=97|pages=110–113|doi=10.1016/j.elecom.2018.11.006|issn=1388-2481|doi-access=free|last1=Murata |first1=Junji |last2=Nishiguchi |first2=Yoshito |last3=Iwasaki |first3=Takeshi }}</ref>