Gallium Arsenide - Preparation and Chemistry

Preparation and Chemistry

In the compound, gallium has a +3 oxidation state. Gallium arsenide can be prepared by direct reaction from the elements, as used in a number of industrial processes:

  • Crystal growth using a horizontal zone furnace in the Bridgman-Stockbarger technique, in which gallium and arsenic vapors react and free molecules deposit on a seed crystal at the cooler end of the furnace.
  • Liquid encapsulated Czochralski (LEC) growth is used for producing high purity single crystals that exhibit semi-insulating characteristics.

Alternative methods for producing films of GaAs include:

  • VPE reaction of gaseous gallium metal and arsenic trichloride:
2 Ga + 2 AsCl3 → 2 GaAs + 3 Cl2
  • MOCVD reaction of trimethylgallium and arsine:
Ga(CH3)3 + AsH3 → GaAs + 3 CH4
  • Molecular beam epitaxy (MBE) of gallium and arsenic:
4 Ga + As4 → 4 GaAs

or

2 Ga + As2 → 2 GaAs

Wet etching of GaAs industrially uses an oxidizing agent such as hydrogen peroxide or bromine water, and the same strategy has been described in a patent relating to processing scrap components containing GaAs where the Ga3+ is complexed with a hydroxamic acid ("HA"), for example::

GaAs + H2O2 + "HA" → "GaA" complex + H3AsO4 + 4 H2O

Oxidation of GaAs occurs in air and degrades performance of the semiconductor. The surface can be passivated by depositing a cubic gallium(II) sulfide layer using a tert-butyl gallium sulfide compound such as (tBuGaS)7.

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