Aluminium nitride

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Aluminium nitride1
Aluminum Nitride powder
Wurtzite polyhedra.png
Identifiers
CAS number 24304-00-5 YesY
PubChem 90455
ChemSpider 81668 YesY
ChEBI CHEBI:50884 YesY
Jmol-3D images Image 1
Properties
Molecular formula AlN
Molar mass 40.9882 g/mol
Appearance white to pale-yellow solid
Density 3.260 g/cm3
Melting point 2200 °C
Boiling point 2517 °C (decomposes)
Solubility in water decomposes in H
2
O
Band gap 6.2 eV (direct)
Electron mobility ~300 cm2/(V·s)
Thermal conductivity 285 W/(m·K)
Refractive index (nD) 1.9–2.2
Structure
Crystal structure Wurtzite
Space group C6v4-P63mc
Coordination
geometry
Tetrahedral
Thermochemistry
Specific
heat capacity
C
740 J·Kg-1 K-1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Aluminum nitride (AlN) is a nitride of aluminum. Its wurtzite phase (w-AlN) is a wide band gap (6.2 eV) semiconductor material, giving it potential application for deep ultraviolet optoelectronics.

History

AlN was first synthesized in 1877, but it was not until the middle of the 1980s that its potential for application in microelectronics was realized due to its relative high thermal conductivity for an electrical insulating ceramic (70–210 W·m−1·K−1 for polycrystalline material, and as high as 285 W·m−1·K−1 for single crystals).2

Stability and chemical properties

Aluminum nitride is stable at high temperatures in inert atmospheres and melts at 2800 °C. In a vacuum, AlN decomposes at ~1800 °C. In the air, surface oxidation occurs above 700°C, and even at room temperature, surface oxide layers of 5-10 nm have been detected. This oxide layer protects the material up to 1370°C. Above this temperature bulk oxidation occurs. Aluminum nitride is stable in hydrogen and carbon dioxide atmospheres up to 980°C.3

The material dissolves slowly in mineral acids through grain boundary attack, and in strong alkalies through attack on the aluminium nitride grains. The material hydrolyzes slowly in water. Aluminum nitride is resistant to attack from most molten salts, including chlorides and cryolite.

Manufacture

AlN is synthesized by the carbothermal reduction of aluminium oxide or by direct nitridation of aluminium. The use of sintering aids, such as Y2O3 or CaO, and hot pressing is required to produce a dense technical grade material.

Applications

Metallization methods are available to allow AlN to be used in electronics applications similar to those of alumina and beryllium oxide.

Currently there is much research into developing light-emitting diodes to operate in the ultraviolet using the gallium nitride based semiconductors and, using the alloy aluminum gallium nitride, wavelengths as short as 250 nm have been achieved. In May 2006, an inefficient AlN LED emission at 210 nm has been reported.4

Among the applications of AlN are

  • opto-electronics,
  • dielectric layers in optical storage media,
  • electronic substrates, chip carriers where high thermal conductivity is essential,
  • military applications,
  • as a crucible to grow crystals of gallium arsenide,
  • steel and semiconductor manufacturing.

Epitaxially grown thin film crystalline aluminium nitride is also used for surface acoustic wave sensors (SAWs) deposited on silicon wafers because of the AlN's piezoelectric properties. One application is an RF filter used in mobile phones called a thin film bulk acoustic resonator (FBAR). This is a MEMS device that uses aluminium nitride sandwiched between two metal layers.5

See also


References

  1. ^ "Aluminum Nitride". Accuratus. Retrieved 2014-01-01. 
  2. ^ "AlN - Aluminium Nitride". Ioffe Database. Sankt-Peterburg: FTI im. A. F. Ioffe, RAN. Retrieved 2014-01-01. 
  3. ^ L. I. Berger (1997). Semiconductor Materials. CRC Press. pp. 123–124. ISBN 0-8493-8912-7. Retrieved 2014-01-01. 
  4. ^ Y. Taniyasu et al. (2006). "An Aluminium Nitride Light-Emitting Diode with a Wavelength of 210 Nanometres". Nature 441 (7091): 325–328. doi:10.1038/nature04760. PMID 16710416. 
  5. ^ "ACPF-7001: Agilent Technologies Announces FBAR Filter for U.S. PCS Band Mobile Phones and Data Cards". wirelessZONE. EN-Genius Network Ltd. 2002-05-27. Archived from the original on 2012-07-30. Retrieved 2008-10-18. 

J.A. Pérez, H. Riascos, J. C. Caicedo, G. Cabrera, L. Yate, (2011) J. Phys.: Conf. Ser. 274 012119 J.A.Pérez et al. Neogranadina Science and Engineering, Vol. 20 (2010) pp.107-115.

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