View source for Indium gallium nitride

{{Short description|Chemical compound}}
{{Use dmy dates|date=December 2024}}

[[File:Uv-LED.jpg|thumb|InGaN blue LED (380–405 nm)]]
[[File:White LED.png|thumb|Spectrum of a white-light LED where GaN or InGaN blue source pumps [[Yttrium aluminium garnet|Ce:YAG]] phosphor]]
'''Indium gallium nitride''' ('''InGaN''', {{chem2|In_{''x''}Ga_{1−''x''}N|auto=1}}) is a [[semiconductor material]] made of a mix of [[gallium nitride]] (GaN) and [[indium nitride]] (InN). It is a ternary [[boron group|group III]]/[[nitrogen group|group V]] [[direct bandgap]] [[semiconductor]]. Its [[bandgap]] can be tuned by varying the amount of indium in the alloy.
In<sub>x</sub>Ga<sub>1−x</sub>N has a direct bandgap span from the infrared (0.69 eV) for InN to the ultraviolet (3.4 eV) of GaN.
The ratio of In/Ga is usually between 0.02/0.98 and 0.3/0.7.<ref>{{cite journal|author=Linti, G.|title=The Group 13 Metals Aluminium, Gallium, Indium and Thallium. Chemical Patterns and Peculiarities. Edited by Simon Aldridge and Anthony J. Downs.Angew. Chem|doi=10.1002/anie.201105633 | volume=50|journal=Angewandte Chemie International Edition|page=11569}}</ref>

==Applications==

===LEDs===
Indium gallium nitride is the light-emitting layer in modern blue and green [[LED]]s and often grown on a [[GaN]] buffer on a transparent substrate as, e.g. [[sapphire]] or [[silicon carbide]]. It has a high [[heat capacity]] and its sensitivity to [[ionizing radiation]] is low (like other [[boron group|group III]] [[nitride]]s), making it also a potentially suitable material for [[solar photovoltaic]] devices, specifically for arrays for [[satellite]]s.

It is theoretically predicted that [[spinodal decomposition]] of indium nitride should occur for compositions between 15% and 85%, leading to In-rich and Ga-rich InGaN regions or clusters. However, only a weak phase [[Segregation in materials|segregation]] has been observed in experimental local structure studies.<ref>{{cite journal|author1=V. Kachkanov |author2=K.P. O'Donnell |author3=S. Pereira |author4=R.W. Martin |journal= Phil. Mag. |volume=87|issue=13|pages= 1999–2017 |year=2007|doi=10.1080/14786430701342164|title=Localization of excitation in InGaN epilayers|bibcode=2007PMag...87.1999K |s2cid=136950050 |url=https://hal.archives-ouvertes.fr/hal-00513828/file/PEER_stage2_10.1080%252F14786430701342164.pdf }}</ref> Other experimental results using cathodoluminescence and [[photoluminescence]] excitation on low In-content InGaN multi-[[quantum well]]s have demonstrated that providing correct material parameters of the InGaN/GaN alloys, theoretical approaches for AlGaN/GaN systems also apply to InGaN nanostructures.<ref>{{cite journal|author=A. Reale1 |author2=A. Di Carlo |author3=A. Vinattieri |author4=M. Colocci |author5=F. Rossi |author6=N. Armani |author7=C. Ferrari |author8=G. Salviati |author9=L. Lazzarini |author10=V. Grillo |title=Investigation of the recombination dynamics in low In-content InGaN MQWs by means of cathodoluminescence and photoluminescence excitation |doi=10.1002/pssc.200460305 | volume=2 |issue=2 |journal=Physica Status Solidi C |pages=817–821|bibcode=2005PSSCR...2..817R |year=2005 }}</ref>

GaN is a defect-rich material with typical dislocation densities<ref>{{cite journal|author=Rak Jun Choi |author2=Hyung Jae Lee |author3=Yoon-bong Hahn |author4=Hyung Koun Cho |title=Structural and optical properties of InGaN/GaN triangular-shape quantum wells with different threading dislocation densities|doi=10.1007/BF02705411 | volume=21|journal=Korean Journal of Chemical Engineering|pages=292–295|year=2004|s2cid=54212942}}</ref> exceeding 10<sup>8</sup> cm<sup>−2</sup>. [[Light emission]] from InGaN layers grown on such GaN buffers used in blue and green LEDs is expected to be attenuated because of non-radiative recombination at such defects.<ref>{{cite web|url=http://handle.dtic.mil/100.2/ADP012939|archive-url=https://web.archive.org/web/20130408135133/http://handle.dtic.mil/100.2/ADP012939|archive-date=8 April 2013| author=P. G. Eliseev|title=Radiative processes in InGaN quantum wells}}</ref> Nevertheless, InGaN [[quantum well]]s, are efficient light emitters in green, blue, white and [[ultraviolet]] [[light-emitting diode]]s and [[diode laser]]s.<ref>{{cite journal|author1=Liang-Yi Chen |author2=Ying-Yuan Huang |author3=Chun-Hsiang Chang |author4=Yu-Hsuan Sun |author5=Yun-Wei Cheng |author6=Min-Yung Ke |author7=Cheng-Pin Chen |author8=JianJang Huang |title=High performance InGaN/GaN nanorod light emitting diode arrays fabricated by nanosphere lithography and chemical mechanical polishing processes|doi=10.1364/OE.18.007664 | volume=18|issue=8 |journal=Optics Express|pages=7664–7669|bibcode=2010OExpr..18.7664C|year=2010 |pmid=20588606 |doi-access=free }}</ref><ref>{{cite web|author1=HJ Chang |author2=et alter |title=Strong luminescence from strain relaxed InGaN/GaN nanotips for highly efficient light emitters|url=http://morkoc.vcu.edu/publications/160326InGaN-GaN-nanotips.pdf |access-date=20 September 2013}}</ref><ref>{{cite journal|author=C Skierbiszewski1,2, P Perlin1,2, I Grzegory, Z R Wasilewski, M Siekacz, A Feduniewicz, P Wisniewski, J Borysiuk, P Prystawko, G Kamler, T Suski and S Porowski|title=High power blue–violet InGaN laser diodes grown on bulk GaN substrates by plasma-assisted molecular beam epitaxy|doi=10.1088/0268-1242/20/8/030 | volume=20|issue=8|journal=Semiconductor Science and Technology|pages=809–813|bibcode=2005SeScT..20..809S|year=2005|s2cid=97464128 }}</ref> The indium-rich regions have a lower bandgap than the surrounding material and create regions of reduced potential energy for charge carriers. Electron-hole pairs are trapped there and recombine with emission of light, instead of diffusing to crystal defects where the recombination is non-radiative. Also, self-consistent computer simulations have shown that radiative recombination is focused where regions are rich of indium.<ref>{{cite journal|first=F. |last=Sacconi|first2=M. |last2=Auf der Maur|first3=A. |last3=Pecchia|first4=M. |last4=Lopez|first5=A. |last5=Di Carlo|journal= Physica Status Solidi C|volume=9 |issue=5| pages= 1315–1319 |year=2012|doi=10.1002/pssc.201100205 |title=Optoelectronic properties of nanocolumnar InGaN/GaN quantum disk LEDs|bibcode=2012PSSCR...9.1315S|doi-access=free}}</ref>

The emitted wavelength, dependent on the material's band gap, can be controlled by the GaN/InN ratio, from near ultraviolet for 0.02In/0.98Ga through 390&nbsp;nm for 0.1In/0.9Ga, violet-blue 420&nbsp;nm for 0.2In/0.8Ga, to blue 440&nbsp;nm for 0.3In/0.7Ga, to red for higher ratios and also by the thickness of the InGaN layers which are typically in the range of 2–3 [[Nanometer|nm]]{{Citation needed|reason=Reliable source needed for the whole sentence|date=February 2017}}. However, atomistic simulations results have shown that emission energies have a minor dependence on small variations of device dimensions.<ref>{{cite journal|author=M. Lopez, F. Sacconi, M. Auf der Maur, A. Pecchia, A. Di Carlo. "Atomistic simulation of InGaN/GaN quantum disk LEDs" |journal= Optical and Quantum Electronics |volume= 44 |issue=3|pages= 89–94|year=2012|doi=10.1007/s11082-012-9554-3 |title=Atomistic simulation of InGaN/GaN quantum disk LEDs|s2cid= 126339984 }}</ref> Studies based on device simulation have shown that it could be possible to increase InGaN/GaN LED efficiency using band gap engineering, especially for green LEDs.<ref>{{cite journal|author= M. Auf der Maur, K. Lorenz and A. Di Carlo. "Band gap engineering approaches to increase InGaN/GaN LED efficiency" |journal= Physica Status Solidi C|volume=44 |issue=3–5| pages= 83–88 |year=2012|doi=10.1007/s11082-011-9536-x |title=Band gap engineering approaches to increase InGaN/GaN LED efficiency|s2cid= 11753092}}</ref>

===Photovoltaics===
The ability to perform bandgap engineering with InGaN over a range that provides a good spectral match to sunlight, makes InGaN suitable for [[solar photovoltaic cell]]s.<ref>{{cite journal | last1 = McLaughlin | first1 = D.V.P. | last2 = Pearce | first2 = J.M. | year = 2013 | title = Progress in Indium Gallium Nitride Materials for Solar Photovoltaic Energy Conversion | url = https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1008&context=materials_fp| journal = Metallurgical and Materials Transactions A | volume = 44 | issue = 4| pages = 1947–1954 | doi = 10.1007/s11661-013-1622-1 | bibcode = 2013MMTA...44.1947M | s2cid = 13952749 }}</ref><ref>{{cite journal | last1 = Bhuiyan | first1 = A. | last2 = Sugita | first2 = K. | last3 = Hashimoto | first3 = A. | last4 = Yamamoto | first4 = A. | year = 2012 | title = InGaN Solar Cells: Present State of the Art and Important Challenges | journal = IEEE Journal of Photovoltaics | volume = 2 | issue = 3| pages = 276–293 | doi = 10.1109/JPHOTOV.2012.2193384 | s2cid = 22027530 }}</ref> It is possible to grow multiple layers with different bandgaps, as the material is relatively insensitive to defects introduced by a lattice mismatch between the layers. A two-layer multijunction cell with bandgaps of 1.1 [[electronvolt|eV]] and 1.7 eV can attain a theoretical 50% maximum efficiency, and by depositing multiple layers tuned to a wide range of bandgaps an efficiency up to 70% is theoretically expected.<ref>[http://www.lbl.gov/Science-Articles/Archive/MSD-perfect-solar-cell-2.html A nearly perfect solar cell, part 2] {{Webarchive|url=https://web.archive.org/web/20200917000213/https://www2.lbl.gov/Science-Articles/Archive/MSD-perfect-solar-cell-2.html |date=17 September 2020 }}. Lbl.gov. Retrieved 2011-11-07.</ref>

Significant photoresponse was obtained from experimental InGaN single-junction devices.<ref>{{cite journal | last1 = Zeng | first1 = S. W. | display-authors = etal   | year = 2009 | title = Substantial photo-response of InGaN p–i–n homojunction solar cells | journal = Semicond. Sci. Technol. | volume = 24 | issue = 5| page = 055009 | doi = 10.1088/0268-1242/24/5/055009 | bibcode = 2009SeScT..24e5009Z| s2cid = 97236733 }}</ref><ref>{{cite journal | last1 = Sun | first1 = X. | display-authors = etal   | year = 2008 | title = Photoelectric characteristics of metal/InGaN/GaN heterojunction structure | journal = J. Phys. D | volume = 41 | issue = 16| page = 165108 | doi = 10.1088/0022-3727/41/16/165108 | bibcode = 2008JPhD...41p5108S| s2cid = 120480676 }}</ref> In addition to controlling the optical properties,<ref>{{cite journal|author1=Dirk V. P. McLaughlin |author2=J.M. Pearce |title=Analytical Model for the Optical Functions of Indium Gallium Nitride with Application to Thin Film Solar Photovoltaic Cells|journal= Materials Science and Engineering: B|volume= 177 |issue=2 |pages= 239–244 |year=2012|doi=10.1016/j.mseb.2011.12.008|arxiv=1201.2911|s2cid=95949405 }}</ref> which results in band gap engineering, photovoltaic device performance can be improved by engineering the microstructure of the material to increase the optical path length and provide light trapping. Growing nanocolumns on the device can further result in resonant interaction with light,<ref>{{Cite journal | last1 = Cao | first1 = L. | last2 = White | first2 = J. S. | last3 = Park | first3 = J. S. | last4 = Schuller | first4 = J. A. | last5 = Clemens | first5 = B. M. | last6 = Brongersma | first6 = M. L. | doi = 10.1038/nmat2477 | title = Engineering light absorption in semiconductor nanowire devices | journal = Nature Materials | volume = 8 | issue = 8 | pages = 643–647 | year = 2009 | pmid =  19578337| bibcode = 2009NatMa...8..643C }}</ref> and InGaN nanocolumns have been successfully deposited on {{chem|SiO|2}} using plasma enhanced evaporation.<ref>{{cite journal|author1=S. Keating |author2=M.G. Urquhart |author3=D.V.P. McLaughlin |author4=J.M. Pearce |title=Effects of Substrate Temperature on Indium Gallium Nitride Nanocolumn Crystal Growth|journal= Crystal Growth & Design|volume= 11 |issue=2|pages= 565–568|year=2011|doi=10.1021/cg101450n|url=http://qspace.library.queensu.ca/handle/1974/6430|arxiv=1203.0645|s2cid=53506014 }}</ref> Nanorod growth may also be advantageous in the reduction of treading dislocations which may act as charge traps reducing solar cell efficiency
<ref>{{Cite journal | last1 = Cherns | first1 = D. | last2 = Webster | first2 = R. F. | last3 = Novikov | first3 = S. V. | last4 = Foxon | first4 = C. T. | last5 = Fischer | first5 = A. M. | last6 = Ponce| first6 = F. A. | last7 = Haigh | first7 = S. J. | doi = 10.1088/0957-4484/25/21/215705 | title = Compositional variations in In0.5Ga0.5N nanorods grown by molecular beam epitaxy | journal = Nanotechnology | volume = 25 | issue = 21 | page = 215705 | year = 2014| pmid = 24785272 | bibcode = 2014Nanot..25u5705C | doi-access = free }}</ref>

Metal-modulated [[epitaxy]] allows controlled atomic layer-by-layer growth of thin films with almost ideal characteristics enabled by strain relaxation at the first atomic layer. The crystal's lattice structures match up, resembling a perfect crystal, with corresponding luminosity. The crystal had indium content ranging from x ~ 0.22 to 0.67. Significant improvement in the crystalline quality and optical properties began at x ~ 0.6. Films were grown at ~400&nbsp;°C to facilitate indium incorporation and with precursor modulation to enhance surface morphology and metal adlayer diffusion. These findings should contribute to the development of growth techniques for nitride semiconductors under high lattice misfit conditions.<ref>{{cite web|url=http://www.kurzweilai.net/controlled-atomic-layer-crystal-growth-is-breakthrough-for-solar-cell-efficiency |title=Controlled atomic-layer crystal growth is 'breakthrough' for solar-cell efficiency |publisher=KurzweilAI |access-date=2013-10-31}}</ref><ref>{{Cite journal | last1 = Fischer | first1 = A. M. | last2 = Wei | first2 = Y. O. | last3 = Ponce | first3 = F. A. | last4 = Moseley | first4 = M. | last5 = Gunning | first5 = B. | last6 = Doolittle | first6 = W. A. | doi = 10.1063/1.4822122 | title = Highly luminescent, high-indium-content InGaN film with uniform composition and full misfit-strain relaxation | journal = Applied Physics Letters | volume = 103 | issue = 13 | page = 131101 | year = 2013 | bibcode = 2013ApPhL.103m1101F | url = https://zenodo.org/record/895544 }}</ref>

===Quantum heterostructures===
[[Quantum heterostructure]]s are often built from [[gallium nitride|GaN]] with InGaN active layers. InGaN can be combined with other materials, e.g. [[gallium nitride|GaN]], [[aluminium gallium nitride|AlGaN]], on [[silicon carbide|SiC]], [[sapphire]] and even [[silicon]].

===Nanorods===
[[nanorod#InGaN/GaN nanorods|InGaN nanorod LEDs]] are three-dimensional structures with a larger emitting surface, better efficiency and greater light emission compared to planar LEDs {{Citation needed|reason=Reliable source needed for the whole sentence|date=August 2023}}.

==Safety and toxicity==
The toxicology of InGaN has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The [[environment, health and safety]] aspects of indium gallium nitride sources (such as [[trimethylindium]], [[trimethylgallium]] and [[ammonia]]) and industrial hygiene monitoring studies of standard [[MOVPE]] sources have been reported recently in a review.<ref>{{cite journal|title=Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors|author1=D V Shenai-Khatkhate |author2=R Goyette |author3=R L DiCarlo |author4=G Dripps |journal= Journal of Crystal Growth|volume= 1–4|issue=1–4 |pages=816–821|year=2004|doi=10.1016/j.jcrysgro.2004.09.007|bibcode=2004JCrGr.272..816S}}</ref>

==See also==
* [[Indium gallium phosphide]]
* [[Indium gallium arsenide]]

==References==
{{reflist}}

{{Indium compounds}}
{{Gallium compounds}}
{{Nitrides}}

[[Category:Indium compounds]]
[[Category:Gallium compounds]]
[[Category:Nitrides]]
[[Category:III-V semiconductors]]
[[Category:III-V compounds]]
[[Category:Light-emitting diode materials]]