Gallium phosphide


Gallium phosphide (GaP), a phosphide of gallium, is a compound semiconductor material with an indirect band gap of 2.24 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.

Gallium phosphide
GaP ingots.jpg
GaP ingots (impure)
GaP wafer (electronic device quality)
IUPAC name
Gallium phosphide
Other names
Gallium(III) phosphide
  • 12063-98-8 checkY
3D model (JSmol)
  • Interactive image
  • Interactive image
  • 74803 checkY
ECHA InfoCard 100.031.858 Edit this at Wikidata
  • 82901
RTECS number
  • LW9675000
  • 3J421F73DV checkY
  • DTXSID60894184 Edit this at Wikidata
  • InChI=1S/Ga.P checkY
  • InChI=1/Ga.P/rGaP/c1-2
  • [Ga]#P
  • [Ga+3].[P-3]
Molar mass 100.697 g/mol[1]
Appearance pale orange solid
Odor odorless
Density 4.138 g/cm3[1]
Melting point 1,457 °C (2,655 °F; 1,730 K)[1]
Band gap 2.24 eV (indirect, 300 K)[2]
Electron mobility 300 cm2/(V·s) (300 K)[2]
-13.8×10−6 cgs[2]
Thermal conductivity 0.752 W/(cm·K) (300 K)[1]
2.964 (10 µm), 3.209 (775 nm), 3.590 (500 nm), 5.05 (354 nm)[3]
Zinc blende
a = 544.95 pm[4]
−88.0 kJ/mol[5]
NFPA 704 (fire diamond)
Flash point 110 °C (230 °F; 383 K)
Related compounds
Other anions
Gallium nitride
Gallium arsenide
Gallium antimonide
Other cations
Aluminium phosphide
Indium phosphide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

GaP has a microhardness of 9450 N/mm2, a Debye temperature of 446 K (173 °C), and a thermal expansion coefficient of 5.3 ×10−6 K−1 at room temperature.[4] Sulfur, silicon or tellurium are used as dopants to produce n-type semiconductors. Zinc is used as a dopant for the p-type semiconductor.

Gallium phosphide has applications in optical systems.[6][7][8] Its static dielectric constant is 11.1 at room temperature.[2] Its refractive index varies between ~3.2 and 5.0 across the visible range, which is higher than in most other semiconducting materials.[3] 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 diodesEdit

Gallium phosphide has been used in the manufacture of low-cost red, orange, and green light-emitting diodes (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 nm. Nitrogen-doped GaP emits yellow-green (565 nm) light, zinc oxide doped GaP emits red (700 nm).

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

Crystal growthEdit

At temperatures above ~900 °C, gallium phosphide dissociates and the phosphorus escapes as a gas. In crystal growth from a 1500 °C melt (for LED wafers), this must be prevented by holding the phosphorus in with a blanket of molten 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.


  1. ^ a b c d Haynes, p. 4.63
  2. ^ a b c d Haynes, p. 12.85
  3. ^ a b Haynes, p. 12.156
  4. ^ a b Haynes, p. 12.80
  5. ^ Haynes, p. 5.20
  6. ^ Wilson, Dalziel J.; Schneider, Katharina; Hönl, Simon; Anderson, Miles; Baumgartner, Yannick; Czornomaz, Lukas; Kippenberg, Tobias J.; Seidler, Paul (January 2020). "Integrated gallium phosphide nonlinear photonics". Nature Photonics. 14 (1): 57–62. arXiv:1808.03554. doi:10.1038/s41566-019-0537-9. ISSN 1749-4893. S2CID 119357160.
  7. ^ Cambiasso, Javier; Grinblat, Gustavo; Li, Yi; Rakovich, Aliaksandra; Cortés, Emiliano; Maier, Stefan A. (2017-02-08). "Bridging the Gap between Dielectric Nanophotonics and the Visible Regime with Effectively Lossless Gallium Phosphide Antennas". Nano Letters. 17 (2): 1219–1225. doi:10.1021/acs.nanolett.6b05026. hdl:10044/1/45460. ISSN 1530-6984. PMID 28094990.
  8. ^ Rivoire, Kelley; Lin, Ziliang; Hatami, Fariba; Masselink, W. Ted; Vučković, Jelena (2009-12-07). "Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power". Optics Express. 17 (25): 22609–22615. arXiv:0910.4757. doi:10.1364/OE.17.022609. ISSN 1094-4087. PMID 20052186. S2CID 15879811.

Cited sourcesEdit

External linksEdit

  • GaP.
  • Ioffe NSM data archive
  • GaP wafer supplier : Shin-Etsu Chemical Co., Ltd.