Gallium phosphide

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Gallium phosphide
Sphalerite-unit-cell-3D-balls.png
Identifiers
CAS number 12063-98-8 YesY
PubChem 82901
ChemSpider 74803 YesY
RTECS number LW9675000
Jmol-3D images Image 1
Properties
Molecular formula GaP
Molar mass 100.697 g/mol
Appearance pale orange solid
Odor odorless
Density 4.138 g/cm3
Melting point 1,477 °C (2,691 °F; 1,750 K)
Solubility in water insoluble
Band gap 2.26 eV (300 K)
Electron mobility 250 cm2/(V*s) (300 K)
Thermal conductivity 1.1 W/(cm*K) (300 K)
Refractive index (nD) 3.02 (2.48 µm), 3.19 (840 nm), 3.45 (550 nm), 4.30 (262 nm)
Structure
Crystal structure Zinc Blende
Space group T2d-F-43m
Lattice constant a = 545.05 pm
Coordination
geometry
Tetrahedral
Hazards
EU Index Not listed
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored 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 noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Gallium phosphide (GaP), a phosphide of gallium, is a compound semiconductor material with an indirect band gap of 2.26 eV(300K). The polycrystalline material has the appearance of pale orange pieces. Undoped single crystal wafers appear clear orange, but strongly doped wafers appear darker due to free-carrier absorption. It is odorless and insoluble in water.

Sulfur 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. Its refractive index is between 4.30 at 262 nm (UV), 3.45 at 550 nm (green) and 3.19 at 840 nm (IR).[1]

Light-emitting diodes[edit]

Gallium phosphide is used in the manufacture of low-cost red, orange, and green light-emitting diodes (LEDs) with low to medium brightness since the 1960s. It has a relatively short life at higher current and its lifetime is sensitive to temperature. 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.

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.

See also[edit]

Related materials[edit]

Alloys[edit]

External links[edit]

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