Gallium arsenide

From ArticleWorld

Gallium arsenide, with the chemical formula GaAs is a compound formed as a result of a chemical reaction between the elements gallium and arsenic. This chemical substance finds use in a number of electronic devices. Being an important semiconductor, it has certain advantages over silicon in terms of its electronic properties.

Physical properties of gallium arsenide

Crystals of gallium arsenide are cubic in shape and dark grey in colour. Under normal conditions of temperature and pressure the compound exists in the solid state and melts at a temperature of about 1240°C. It has a specific gravity of 5.318. Gallium arsenide is known to be toxic in nature. It is a carcinogenic substance as well.

Electronic properties of gallium arsenide

Gallium arsenide has an electron mobility of 9200cm ²/V-s, which is greater than that of silicon. The saturated electron velocity is high as well. The hole mobility of this compound is about 400cm²/V-s. At room temperature (about 27 º C) gallium arsenide has an energy band gap of 1.424 eV. These electronic properties, plus the fact that GaAs devices generate lesser noise than silicon devices at high frequencies have made this compound extremely important for use at frequencies well beyond 250 GHz.

Since GaAs has a higher breakdown voltage than silicon and hence is suitable for operations at higher power levels.

Gallium arsenide has a faster switching speed than silicon and was proposed to be used in computing devices. However, the high cost of this compound has made it difficult to be put to use in such fields.

Applications of gallium arsenide

Single crystals of gallium arsenide are prepared by the Bridgeman technique. The resulting compound can be alloyed with other substances like aluminium arsenide and grown to a desired thickness using the process of molecular beam epitaxy.

Gallium arsenide is widely used in the manufacture of equipment used in mobile, radar and satellite communication. Infrared light emitting diodes and laser diodes also use GaAs because of its desirable electronic properties. Triple junction solar cells deploying this compound along with germanium and indium gallium phosphide have excellent efficiencies. Such cells have been put to use in robots exploring the Martian surface.

There have been suggestions to use gallium arsenide in manufacturing computing devices, but silicon continues to be popular in that respect. This is because of silicon being inexpensive and easily available, being the most abundant element in the Earth’s crust. Also, silicon possesses greater strength and is easier to process.