Gallium nitride

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Crystal structure
Structure of gallium nitride
__ Ga 3+      __ N 3−
General
Surname Gallium nitride
Ratio formula GaN
Brief description

yellow, odorless solid

External identifiers / databases
CAS number 25617-97-4
EC number 247-129-0
ECHA InfoCard 100,042,830
PubChem 117559
Wikidata Q411713
properties
Molar mass 83.72 g mol −1
Physical state

firmly

density

6.1 g cm −3

solubility

almost insoluble in water

safety instructions
GHS labeling of hazardous substances
07 - Warning

Caution

H and P phrases H: 317
P: 280
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Gallium nitride ( GaN ) is a made of gallium and nitrogen existing III-V semiconductor with a large band gap (wide bandgap) in the optoelectronics particularly for blue and green light emitting diodes (LED), and as an alloy component at high-electron-mobility transistors (HEMT ), a type of junction field effect transistor (JFET), is used. In addition, the material is suitable for various sensor applications.

history

The material was synthesized for the first time around 1930 and was first grown epitaxially as a layer in 1969 by Maruska and Tietjen using hydride gas phase epitaxy . 1971 succeeded Manasevit, Erdmann and Simpson for the first time metal organic chemical vapor deposition ( English metal-organic chemical vapor deposition , MOCVD) growth of GaN, what can regarded as an important step in the further development.

properties

GaN preferably crystallizes in the ( hexagonal ) wurtzite structure , the cubic zinc blende structure is not stable.

property value
Crystal system hexagonal (cubic)
colour colorless, white, gray, yellow
shine Glass gloss
opacity transparent to opaque
Cleavage Well
frequent crystal orientation of substrates (0001), {1-101}
Refractive index approx. 2.5 at 400  nm
Crystal structure Wurtzite structure (stable), zinc blende structure , rock salt structure (high pressure phase)
Lattice constant Wurtzite: c  = 0.5185 nm, a  = 0.3189 nm; Zinc  screen : a = 0.452 nm
Band gap Wurtzite: 3.44  eV at room temperature and 3.50 eV at T = 10 K; Zincblende: 3.2 eV

The compound is slowly dissolved by hot concentrated sulfuric acid and hot concentrated sodium hydroxide solution , but not by concentrated hydrochloric acid , nitric acid and aqua regia . It is air-resistant and, depending on the atmosphere, temperature and pressure, decomposes at elevated temperatures to form molecular nitrogen and gallium. Without special countermeasures, this decomposition begins in the atmosphere from approx. 600 ° C.

Manufacturing

Gallium nitride single crystal, approx. 3 mm long

The main problem in the production of GaN-based components was and is due to the difficulty of producing large single crystals from GaN in order to produce high-quality GaN wafers from them. Therefore, foreign substrates still have to be used, mainly sapphire and SiC. The quality of the (heteroepitaxial) layers on foreign substrates was greatly enhanced by the work of the Akasaki and Nakamura groups at the end of the 1980s. Another challenge is the p-doping of the semiconductor material, which is necessary for almost all optoelectronic components. It was first achieved by Akasaki's group in 1988, and then in 1992 by Shuji Nakamura with a modified approach.

GaN single crystals are today primarily by means of hydride vapor phase epitaxy (Engl. Hydride vapor phase epitaxy ) made, which is promoted worldwide by a handful of companies technologically. First of all, gaseous hydrogen chloride reacts with liquid gallium at a temperature of approx. 880 ° C to form gallium chloride . In a reaction zone, the gallium chloride is brought close to a GaN crystal nucleus at temperatures between 1000 and 1100 ° C. Here the gallium chloride reacts with the incoming ammonia , releasing hydrogen chloride to form crystalline gallium nitride. Under optimal conditions, the HVPE process can meanwhile produce crystals with a diameter of up to 50 mm and a thickness of a few millimeters.

In the laboratory, gallium nitride is produced by reacting gallium with ammonia at 1100 ° C

or produced by ammonolysis of ammonium hexafluorogallate at 900 ° C:

Areas of application

This led to the first commercial blue LED , marketed by Nichia since 1993 , and later to the first blue semiconductor laser (1997, Nichia). Until then, blue LEDs were based on the material silicon carbide , which, as an indirect semiconductor, is poorly suited for efficient light emission. With a higher proportion of indium in the active zone of the GaInN quantum films, green and yellow light emission is also possible. However, the efficiency of such LEDs increasingly decreases with higher In content due to several physical and chemical facts.

In addition to the foreign substrate sapphire , GaN can now also be produced on silicon carbide (SiC) and on silicon (Si). From a purely technical point of view, GaN on SiC is advantageous for use in the field of power electronics due to the high thermal conductivity of SiC . However, when compared to silicon, the substrate cost for silicon carbide is significantly higher (about $ 1000 per 4-inch wafer).

The first prototypes of field effect transistors based on gallium nitride with an operating voltage of up to 600 V could be used in switched-mode power supplies and power supplies in 2012 . They allow higher switching frequencies and achieve a higher degree of efficiency in the power supply unit than the more cost-effective silicon-based field effect transistors usually used in this area. GaN is particularly suitable for high-performance high-frequency amplifiers , such as those required for the base stations and the infrastructure of cellular networks , since high frequencies can be processed with high power. In 2017, GaN components were used in around 25% of these applications. For smaller services such as B. in cell phones , components made of GaAs are cheaper to manufacture.

The electrical properties as well as the resistance to heat and radiation give the material strategic importance for military and space applications. This allows z. B. Company takeovers from manufacturers are blocked by governments, such as the planned takeover of Wolfspeed by Infineon in 2016 .

Individual evidence

  1. a b c data sheet gallium nitride from AlfaAesar, accessed on January 29, 2010 ( PDF )(JavaScript required) .
  2. a b data sheet gallium nitride from Sigma-Aldrich , accessed on April 2, 2011 ( PDF ).
  3. ^ HP Maruska, JJ Tietjen: Paramagnetic defects in GaN . In: Appl. Phys. Lett. tape 15 , 1969, p. 327 , doi : 10.1557 / S1092578300001174 (free full text).
  4. HM Manasevit, FM Erdmann, WI Simpson: The use of metal organics in the preparation of semiconductor materials. IV. The nitrides of aluminum and gallium . In: J. Electrochem. Soc . tape 118 , no. 11 , 1971, p. 1864-1868 , doi : 10.1149 / 1.2407853 .
  5. ^ A b Norbert H. Nickel, Robert K. Willardson, Eicke R. Weber : Hydrogen in Semiconductors II . In: Semiconductors & Semimetals . tape 61 . Academic Pr. Inc., 1999, ISBN 0-12-752170-4 ( limited preview in Google Book Search).
  6. Sergey L. Rumyantsev, Michael S. Shur, Michael E. Levinshtein: Materials properties of nitrides: summary . In: International Journal of High Speed ​​Electronics and Systems . tape 14 , no. 1 , 2004, ISSN  0129-1564 , p. 1-19 , doi : 10.1142 / S012915640400220X ( PDF ).
  7. a b Georg Brauer , with the collaboration of Marianne Baudler a . a. (Ed.): Handbook of Preparative Inorganic Chemistry . 3rd, revised edition. tape I . Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , pp. 861 .
  8. David Manners: Dialog enters GaN market. Dialog will start sampling GaN power ICs in Q4 with a fast charging power adapter made on TSMC's 650-volt GaN-on-Silicon process technology. Electronics Weekly, August 30, 2016, accessed September 2, 2016 .
  9. Karin Schneider: Smaller, lighter and more efficient with gallium nitride components. Fraunhofer Institute for Solar Energy Systems ISE, press release from November 7, 2012 from Informationsdienst Wissenschaft (idw-online.de), accessed on August 23, 2015.
  10. a b c Richard Wilson: 5G set to adopt GaN, but military protectionism may hit supply. Gallium nitride (GaN) semiconductor technology looks like being a key element of future wireless infrastructure deployments including 5G. Electronics Weekly , February 8, 2018, accessed February 14, 2018 .
  11. Diana Goovaerts: GaN Gaining Ground in Mobile Wireless Infrastructure Market. Wireless Week, March 27, 2017, accessed April 1, 2017 .
  12. Paul Motor, Jane Perlez: Concern Grows in US Over China's Drive to Make Chips. The New York Times , February 4, 2016, accessed February 11, 2016 .
  13. Wolfspeed takeover by Infineon failed. heise online, February 17, 2017, accessed on February 14, 2018 .

literature

  • Michinobu Tsuda, Motoaki Iwaya, Satoru Kamiyama, Hiroshi Amano, Isamu Akasaki: Metalorganic vapor phase epitaxy (MOVPE) of nitride semiconductor at high growth rate, epitaxial substrates therefrom, and semiconductor devices using them. Jpn. Kokai Tokkyo Koho, 2006.
  • Tosja K. Zywietz: Thermodynamic and kinetic properties of gallium nitride surfaces. Berlin 2000, ISBN 978-3-934479-10-4 .
  • Sergey L. Rumyantsev, Michael S. Shur, Michael E. Levinshtein: Materials properties of nitrides: summary . In: International Journal of High Speed ​​Electronics and Systems . tape 14 , no. 1 , 2004, ISSN  0129-1564 , p. 1-19 , doi : 10.1142 / S012915640400220X ( PDF ).
  • S. Fernández-Garrido, G. Koblmüller, E. Calleja, JS Speck: In situ GaN decomposition analysis by quadrupole mass spectrometry and reflection high-energy electron diffraction . In: Journal of Applied Physics . tape 104 , no. 3 , 2008, p. 033541 , doi : 10.1063 / 1.2968442 ( PDF ).

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