Gallium phosphide (GaP), aphosphide ofgallium, is acompoundsemiconductor material with anindirectband 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 (impure)
GaP wafer (electronic device quality)
Names
IUPAC name Gallium phosphide
Other names Gallium(III) phosphide gallanylidynephosphane
Identifiers
CAS Number	12063-98-8 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	74803 Y
ECHA InfoCard	100.031.858
PubChemCID	82901
RTECS number	LW9675000
UNII	3J421F73DV Y
CompTox Dashboard(EPA)	DTXSID60894184
InChI InChI=1S/Ga.P Y Key: HZXMRANICFIONG-UHFFFAOYSA-N Y InChI=1/Ga.P/rGaP/c1-2 Key: HZXMRANICFIONG-ZZOGKRAHAQ
SMILES [Ga]#P [Ga+3].[P-3]
Properties
Chemical formula	GaP
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]
Solubility in water	insoluble
Band gap	2.24 eV (indirect, 300 K)[2]
Electron mobility	300 cm2/(V·s) (300 K)[2]
Magnetic susceptibility (χ)	−13.8×10−6 cgs[2]
Thermal conductivity	0.752 W/(cm·K) (300 K)[1]
Refractive index (nD)	2.964 (10 µm), 3.209 (775 nm), 3.590 (500 nm), 5.05 (354 nm)[3]
Structure
Crystal structure	Zinc blende
Space group	T2d-F-43m
Lattice constant	a = 544.95 pm[4]
Coordination geometry	Tetrahedral
Thermochemistry
Std enthalpy of formation(ΔfH⦵298)	−88.0 kJ/mol[5]
Hazards
NFPA 704 (fire diamond)	3 1 0
Flash point	110 °C (230 °F; 383 K)
Related compounds
Otheranions	Gallium nitride Gallium arsenide Gallium antimonide
Othercations	Aluminium phosphide Indium phosphide
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

GaP has a microhardness of 9450 N/mm², aDebye temperature of 446 K (173 °C), and athermal expansion coefficient of 5.3×10⁻⁶ K⁻¹ at room temperature.^[4]Sulfur,silicon ortellurium are used asdopants to producen-type semiconductors.Zinc is used as a dopant for thep-type semiconductor.

Gallium phosphide has applications in optical systems.^[6][7][8] Its staticdielectric constant is 11.1 at room temperature.^[2] Itsrefractive 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 asdiamond, or non-oxide lenses such aszinc sulfide.

Gallium phosphide has been used in the manufacture of low-cost red, orange, and greenlight-emitting diodes (LEDs) with low to medium brightness since the 1960s. It is used standalone or together withgallium 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.

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 moltenboric oxide in inert gas pressure of 10–100 atmospheres. The process is called liquid encapsulated Czochralski (LEC) growth, an elaboration of theCzochralski process used for silicon wafers.

• Haynes, William M., ed. (2016).CRC Handbook of Chemistry and Physics (97th ed.).CRC Press.ISBN 9781498754293.

• GaP. refractiveindex.info
• Ioffe NSM data archive