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Indium gallium nitride

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InGaN blue LED (380–405 nm)
Spectrum of a white-light LED where GaN or InGaN blue source pumpsCe:YAGphosphor

Indium gallium nitride(InGaN,InxGa1−xN) is asemiconductor materialmade of a mix ofgallium nitride(GaN) andindium nitride(InN). It is a ternarygroup III/group Vdirect bandgapsemiconductor.Itsbandgapcan be tuned by varying the amount of indium in the alloy. InxGa1−xN 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.[1]

Applications

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LEDs

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Indium gallium nitride is the light-emitting layer in modern blue and greenLEDsand often grown on aGaNbuffer on a transparent substrate as, e.g.sapphireorsilicon carbide.It has a highheat capacityand its sensitivity toionizing radiationis low (like othergroup IIInitrides), making it also a potentially suitable material forsolar photovoltaicdevices, specifically for arrays forsatellites.

It is theoretically predicted thatspinodal decompositionof 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 phasesegregationhas been observed in experimental local structure studies.[2]Other experimental results using cathodoluminescence andphotoluminescenceexcitation on low In-content InGaN multi-quantum wellshave demonstrated that providing correct material parameters of the InGaN/GaN alloys, theoretical approaches for AlGaN/GaN systems also apply to InGaN nanostructures.[3]

GaN is a defect-rich material with typical dislocation densities[4]exceeding 108cm−2.Light emissionfrom 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.[5]Nevertheless, InGaNquantum wells,are efficient light emitters in green, blue, white andultravioletlight-emitting diodesanddiode lasers.[6][7][8]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.[9]

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 nm for 0.1In/0.9Ga, violet-blue 420 nm for 0.2In/0.8Ga, to blue 440 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 2–3nm[citation needed].However, atomistic simulations results have shown that emission energies have a minor dependence on small variations of device dimensions.[10]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.[11]

Photovoltaics

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The ability to perform bandgap engineering with InGaN over a range that provides a good spectral match to sunlight, makes InGaN suitable forsolar photovoltaic cells.[12][13]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 1.1eVand 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.[14]

Significant photoresponse was obtained from experimental InGaN single-junction devices.[15][16]In addition to controlling the optical properties,[17]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,[18]and InGaN nanocolumns have been successfully deposited onSiO
2using plasma enhanced evaporation.[19]Nanorod growth may also be advantageous in the reduction of treading dislocations which may act as charge traps reducing solar cell efficiency [20]

Metal-modulatedepitaxyallows 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 °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.[21][22]

Quantum heterostructures

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Quantum heterostructuresare often built fromGaNwith InGaN active layers. InGaN can be combined with other materials, e.g.GaN,AlGaN,onSiC,sapphireand evensilicon.

Nanorods

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InGaN nanorod LEDsare three-dimensional structures with a larger emitting surface, better efficiency and greater light emission compared to planar LEDs[citation needed].

Safety and toxicity

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The toxicology of InGaN has not been fully investigated. The dust is an irritant to skin, eyes and lungs. Theenvironment, health and safetyaspects of indium gallium nitride sources (such astrimethylindium,trimethylgalliumandammonia) and industrial hygiene monitoring studies of standardMOVPEsources have been reported recently in a review.[23]

See also

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References

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  1. ^Linti, G. "The Group 13 Metals Aluminium, Gallium, Indium and Thallium. Chemical Patterns and Peculiarities. Edited by Simon Aldridge and Anthony J. Downs.Angew. Chem".Angewandte Chemie International Edition.50:11569.doi:10.1002/anie.201105633.
  2. ^V. Kachkanov; K.P. O'Donnell; S. Pereira; R.W. Martin (2007)."Localization of excitation in InGaN epilayers"(PDF).Phil. Mag.87(13): 1999–2017.Bibcode:2007PMag...87.1999K.doi:10.1080/14786430701342164.S2CID136950050.
  3. ^A. Reale1; A. Di Carlo; A. Vinattieri; M. Colocci; F. Rossi; N. Armani; C. Ferrari; G. Salviati; L. Lazzarini; V. Grillo (2005). "Investigation of the recombination dynamics in low In-content InGaN MQWs by means of cathodoluminescence and photoluminescence excitation".Physica Status Solidi C.2(2): 817–821.Bibcode:2005PSSCR...2..817R.doi:10.1002/pssc.200460305.{{cite journal}}:CS1 maint: numeric names: authors list (link)
  4. ^Rak Jun Choi; Hyung Jae Lee; Yoon-bong Hahn; Hyung Koun Cho (2004). "Structural and optical properties of InGaN/GaN triangular-shape quantum wells with different threading dislocation densities".Korean Journal of Chemical Engineering.21:292–295.doi:10.1007/BF02705411.S2CID54212942.
  5. ^P. G. Eliseev."Radiative processes in InGaN quantum wells".Archived fromthe originalon 8 April 2013.
  6. ^Liang-Yi Chen; Ying-Yuan Huang; Chun-Hsiang Chang; Yu-Hsuan Sun; Yun-Wei Cheng; Min-Yung Ke; Cheng-Pin Chen; JianJang Huang (2010)."High performance InGaN/GaN nanorod light emitting diode arrays fabricated by nanosphere lithography and chemical mechanical polishing processes".Optics Express.18(8): 7664–7669.Bibcode:2010OExpr..18.7664C.doi:10.1364/OE.18.007664.PMID20588606.
  7. ^HJ Chang; et alter."Strong luminescence from strain relaxed InGaN/GaN nanotips for highly efficient light emitters"(PDF).Retrieved20 September2013.
  8. ^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 (2005). "High power blue–violet InGaN laser diodes grown on bulk GaN substrates by plasma-assisted molecular beam epitaxy".Semiconductor Science and Technology.20(8): 809–813.Bibcode:2005SeScT..20..809S.doi:10.1088/0268-1242/20/8/030.S2CID97464128.{{cite journal}}:CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  9. ^Sacconi, F.; Auf der Maur, M.; Pecchia, A.; Lopez, M.; Di Carlo, A. (2012)."Optoelectronic properties of nanocolumnar InGaN/GaN quantum disk LEDs".Physica Status Solidi C.9(5): 1315–1319.Bibcode:2012PSSCR...9.1315S.doi:10.1002/pssc.201100205.
  10. ^M. Lopez, F. Sacconi, M. Auf der Maur, A. Pecchia, A. Di Carlo. "Atomistic simulation of InGaN/GaN quantum disk LEDs" (2012). "Atomistic simulation of InGaN/GaN quantum disk LEDs".Optical and Quantum Electronics.44(3): 89–94.doi:10.1007/s11082-012-9554-3.S2CID126339984.{{cite journal}}:CS1 maint: multiple names: authors list (link)
  11. ^M. Auf der Maur, K. Lorenz and A. Di Carlo. "Band gap engineering approaches to increase InGaN/GaN LED efficiency" (2012). "Band gap engineering approaches to increase InGaN/GaN LED efficiency".Physica Status Solidi C.44(3–5): 83–88.doi:10.1007/s11082-011-9536-x.S2CID11753092.
  12. ^McLaughlin, D.V.P.; Pearce, J.M. (2013)."Progress in Indium Gallium Nitride Materials for Solar Photovoltaic Energy Conversion".Metallurgical and Materials Transactions A.44(4): 1947–1954.Bibcode:2013MMTA...44.1947M.doi:10.1007/s11661-013-1622-1.S2CID13952749.
  13. ^Bhuiyan, A.; Sugita, K.; Hashimoto, A.; Yamamoto, A. (2012). "InGaN Solar Cells: Present State of the Art and Important Challenges".IEEE Journal of Photovoltaics.2(3): 276–293.doi:10.1109/JPHOTOV.2012.2193384.S2CID22027530.
  14. ^A nearly perfect solar cell, part 2Archived17 September 2020 at theWayback Machine.Lbl.gov. Retrieved on 2011-11-07.
  15. ^Zeng, S. W.; et al. (2009). "Substantial photo-response of InGaN p–i–n homojunction solar cells".Semicond. Sci. Technol.24(5): 055009.Bibcode:2009SeScT..24e5009Z.doi:10.1088/0268-1242/24/5/055009.S2CID97236733.
  16. ^Sun, X.; et al. (2008). "Photoelectric characteristics of metal/InGaN/GaN heterojunction structure".J. Phys. D.41(16): 165108.Bibcode:2008JPhD...41p5108S.doi:10.1088/0022-3727/41/16/165108.S2CID120480676.
  17. ^Dirk V. P. McLaughlin; J.M. Pearce (2012). "Analytical Model for the Optical Functions of Indium Gallium Nitride with Application to Thin Film Solar Photovoltaic Cells".Materials Science and Engineering: B.177(2): 239–244.arXiv:1201.2911.doi:10.1016/j.mseb.2011.12.008.S2CID95949405.
  18. ^Cao, L.; White, J. S.; Park, J. S.; Schuller, J. A.; Clemens, B. M.; Brongersma, M. L. (2009). "Engineering light absorption in semiconductor nanowire devices".Nature Materials.8(8): 643–647.Bibcode:2009NatMa...8..643C.doi:10.1038/nmat2477.PMID19578337.
  19. ^S. Keating; M.G. Urquhart; D.V.P. McLaughlin; J.M. Pearce (2011)."Effects of Substrate Temperature on Indium Gallium Nitride Nanocolumn Crystal Growth".Crystal Growth & Design.11(2): 565–568.arXiv:1203.0645.doi:10.1021/cg101450n.S2CID53506014.
  20. ^Cherns, D.; Webster, R. F.; Novikov, S. V.; Foxon, C. T.; Fischer, A. M.; Ponce, F. A.; Haigh, S. J. (2014)."Compositional variations in In0.5Ga0.5N nanorods grown by molecular beam epitaxy".Nanotechnology.25(21): 215705.Bibcode:2014Nanot..25u5705C.doi:10.1088/0957-4484/25/21/215705.PMID24785272.
  21. ^"Controlled atomic-layer crystal growth is 'breakthrough' for solar-cell efficiency".KurzweilAI.Retrieved31 October2013.
  22. ^Fischer, A. M.; Wei, Y. O.; Ponce, F. A.; Moseley, M.; Gunning, B.; Doolittle, W. A. (2013)."Highly luminescent, high-indium-content InGaN film with uniform composition and full misfit-strain relaxation".Applied Physics Letters.103(13): 131101.Bibcode:2013ApPhL.103m1101F.doi:10.1063/1.4822122.
  23. ^D V Shenai-Khatkhate; R Goyette; R L DiCarlo; G Dripps (2004). "Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors".Journal of Crystal Growth.1–4(1–4): 816–821.Bibcode:2004JCrGr.272..816S.doi:10.1016/j.jcrysgro.2004.09.007.
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