View source for Gallium phosphide

{{chembox
| verifiedrevid = 477001151
| ImageFile1 = GaP ingots.jpg
| ImageCaption1 = GaP ingots (impure)
| ImageFile2 = GaP-wafer.jpg
| ImageCaption2 = GaP wafer (electronic device quality)
| ImageFile3 = Sphalerite-unit-cell-3D-balls.png
| IUPACName = Gallium phosphide
| OtherNames = Gallium(III) phosphide<br/>gallanylidynephosphane
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 74803
| InChI = 1/Ga.P/rGaP/c1-2
| SMILES = [Ga]#P
| SMILES1 = [Ga+3].[P-3]
| InChIKey = HZXMRANICFIONG-ZZOGKRAHAQ
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Ga.P
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = HZXMRANICFIONG-UHFFFAOYSA-N
| CASNo = 12063-98-8
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 3J421F73DV
| PubChem = 82901
| RTECS = LW9675000
  }}
|Section2={{Chembox Properties 
| Formula = GaP
| MolarMass = 100.697 g/mol<ref name=crc>Haynes, p. 4.63</ref>
| Appearance = pale orange solid
| Odor = odorless
| Density = 4.138 g/cm<sup>3</sup><ref name=crc/>
| MeltingPtC = 1457
| MeltingPt_ref =<ref name=crc/>
| BoilingPtC = 
| Solubility = insoluble
| BandGap = 2.24 eV (indirect, 300 K)<ref name=crc3/>
| ElectronMobility = 300 cm<sup>2</sup>/(V·s) (300 K)<ref name=crc3/>
| ThermalConductivity = 0.752 W/(cm·K) (300 K)<ref name=crc/>
| RefractIndex = 2.964 (10 µm), 3.209 (775 nm), 3.590 (500 nm), 5.05 (354 nm)<ref name=crc4>Haynes, p. 12.156</ref>
| MagSus = −13.8{{e|-6}} cgs<ref name=crc3>Haynes, p. 12.85</ref>
}}
|Section3={{Chembox Structure
| MolShape = 
| CrystalStruct = [[Zincblende (crystal structure)|Zinc blende]]
| SpaceGroup = ''T''<sup>2</sup><sub>d</sub>-''F''-4''3m''
| LattConst_a = 544.95 pm<ref name=crc2>Haynes, p. 12.80</ref>
| Coordination = Tetrahedral
| Dipole =
  }}
|Section5={{Chembox Thermochemistry
| DeltaHf = −88.0 kJ/mol<ref>Haynes, p. 5.20</ref>
| Entropy =
| DeltaGf =
| HeatCapacity =
}}
|Section7={{Chembox Hazards
| MainHazards = 
| NFPA-H = 3
| NFPA-F = 1
| NFPA-R = 0
| NFPA-S = 
| FlashPtC = 110
| AutoignitionPtC = 
  }}
|Section8={{Chembox Related
| OtherAnions = [[Gallium nitride]]<br/>[[Gallium arsenide]]<br/>[[Gallium antimonide]]
| OtherCations = [[Aluminium phosphide]]<br/>[[Indium phosphide]]
  }}
}}
'''Gallium phosphide''' ('''GaP'''), a [[phosphide]] of [[gallium]], is a [[compound semiconductor|compound]] [[semiconductor material]] with an [[indirect bandgap|indirect]] [[band gap]] of 2.24{{nbsp}}[[electronvolt|eV]] at room temperature. Impure polycrystalline material has the appearance of pale orange or grayish pieces. Undoped single crystals are orange, but strongly doped wafers appear darker due to [[free carrier absorption]]. It is odorless and insoluble in water.

GaP has a microhardness of 9450 N/mm<sup>2</sup>, a [[Debye temperature]] of {{convert|446|K|C}}, and a [[thermal expansion]] coefficient of 5.3 {{e|-6}} K<sup>−1</sup> at room temperature.<ref name=crc2/> [[Sulfur]], [[silicon]] or [[tellurium]] are used as [[doping (semiconductors)|dopant]]s to produce [[n-type semiconductor]]s.  [[Zinc]] is used as a dopant for the [[p-type semiconductor]].

Gallium phosphide has applications in optical systems.<ref>{{Cite journal|last1=Wilson|first1=Dalziel J.|last2=Schneider|first2=Katharina|last3=Hönl|first3=Simon|last4=Anderson|first4=Miles|last5=Baumgartner|first5=Yannick|last6=Czornomaz|first6=Lukas|last7=Kippenberg|first7=Tobias J.|last8=Seidler|first8=Paul|date=January 2020|title=Integrated gallium phosphide nonlinear photonics|url=https://www.nature.com/articles/s41566-019-0537-9|journal=Nature Photonics|language=en|volume=14|issue=1|pages=57–62|doi=10.1038/s41566-019-0537-9|issn=1749-4893|arxiv=1808.03554|s2cid=119357160}}</ref><ref>{{Cite journal|last1=Cambiasso|first1=Javier|last2=Grinblat|first2=Gustavo|last3=Li|first3=Yi|last4=Rakovich|first4=Aliaksandra|last5=Cortés|first5=Emiliano|last6=Maier|first6=Stefan A.|date=2017-02-08|title=Bridging the Gap between Dielectric Nanophotonics and the Visible Regime with Effectively Lossless Gallium Phosphide Antennas|journal=Nano Letters|volume=17|issue=2|pages=1219–1225|doi=10.1021/acs.nanolett.6b05026|pmid=28094990|bibcode=2017NanoL..17.1219C |issn=1530-6984|hdl=10044/1/45460|url=https://kclpure.kcl.ac.uk/portal/en/publications/3a9a728c-5b90-45c0-b5cb-54495157d182 |hdl-access=free}}</ref><ref>{{Cite journal|last1=Rivoire|first1=Kelley|last2=Lin|first2=Ziliang|last3=Hatami|first3=Fariba|last4=Masselink|first4=W. Ted|last5=Vučković|first5=Jelena|date=2009-12-07|title=Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power|url=https://www.osapublishing.org/oe/abstract.cfm?uri=oe-17-25-22609|journal=Optics Express|language=EN|volume=17|issue=25|pages=22609–22615|doi=10.1364/OE.17.022609|pmid=20052186|issn=1094-4087|arxiv=0910.4757|bibcode=2009OExpr..1722609R |s2cid=15879811}}</ref> Its static [[dielectric constant]] is 11.1 at room temperature.<ref name=crc3/> Its [[refractive index]] varies between ~3.2 and 5.0 across the visible range, which is higher than in most other semiconducting materials.<ref name=crc4/> In its transparent range, its index is higher than almost any other transparent material, including gemstones such as [[diamond]], or non-oxide lenses such as [[zinc sulfide]].

==Light-emitting diodes==
Gallium phosphide has been used in the manufacture of low-cost red, orange, and green [[light-emitting diode]]s (LEDs) with low to medium brightness since the 1960s. It is used standalone or together with [[gallium arsenide phosphide]].

Pure GaP LEDs emit green light at a wavelength of 555&nbsp;nm. [[Nitrogen]]-doped GaP emits yellow-green (565&nbsp;nm) light, [[zinc oxide]] doped GaP emits red (700&nbsp;nm).

Gallium phosphide is transparent for yellow and red light, therefore GaAsP-on-GaP LEDs are more efficient than GaAsP-on-[[gallium arsenide|GaAs]].

== Crystal growth ==
At temperatures above ~900&nbsp;°C, gallium phosphide dissociates and the phosphorus escapes as a gas. In crystal growth from a 1500&nbsp;°C melt (for LED wafers), this must be prevented by holding the phosphorus in with a blanket of molten [[Boron trioxide|boric oxide]] in inert gas pressure of 10–100 atmospheres.  The process is called liquid encapsulated Czochralski (LEC) growth, an elaboration of the [[Czochralski process]] used for silicon wafers.

== References ==
{{Reflist}}

==Cited sources==
*{{cite book | editor= Haynes, William M. | date = 2016| title = [[CRC Handbook of Chemistry and Physics]] | edition = 97th | publisher = [[CRC Press]] | isbn = 9781498754293}}

==External links==
*[https://refractiveindex.info/?shelf=main&book=GaP&page=Aspnes GaP]. refractiveindex.info
* [http://www.ioffe.rssi.ru/SVA/NSM/Semicond/GaP/index.html Ioffe NSM data archive]

{{Gallium compounds}}
{{Phosphides}}

[[Category:III-V semiconductors]]
[[Category:Optical materials]]
[[Category:Gallium compounds]]
[[Category:Phosphides]]
[[Category:III-V compounds]]
[[Category:Light-emitting diode materials]]
[[Category:Zincblende crystal structure]]