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.
Read more about this topic: Gallium Arsenide
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