Gallium Arsenide

The elements known as gallium and arsenic form gallium arsenide. It is used in the manufacture of monolithic microwave integrated circuits, microwave frequency integrated circuits, infrared light emitting diodes, laser diodes, solar cells, and optical windows.

Chemistry of Gallium Arsenide

When in the compound form, gallium has a +3 oxidation state, which means that it is a positively charged ion. To make the compound, there has to be a direct reaction between the two elements. Some of the most common industrial processes are:

• Using a horizontal furnace to grow crystals. Gallium and arsenic vapors react when the Bridgman-Stockbarger technique is used. The free molecules that come from this reaction deposit on a seed crystal.
• Liquid Encapsulated Czochralski (LEC) growth can be used for making very pure crystals that have semi-insulating traits.
• 2 Ga + 2 AsCl3 ? 2GaAs + 3Cl2. This means that gaseous gallium metal is reacted with arsenic trichloride, which creates gallium arsenide and chlorine.
• Ga(CH3)3 + AsH3 ? GaAs + 3CH4. This means that trimethylgallium is mixed with arsine. When this happens, gallium arsenide is created with excess methyl.

Gallium Arsenide v. Silicon

There are advantages to using both GaAs and Silicon. GaAs has an incredibly saturated electron velocity. This allows transistors made from it to function at frequencies in excess of 250 GHz. On top of that, heat does not affect GaAs devices. Finally, GaAs devices generate significantly less noise than silicon when they are operating at high frequencies.

On the other hand, silicon is far cheaper to process. Silicon’s abundance and minimal cost cause it to be most developers’ preferred option. Silicon dioxide is also chosen over GaAs because it is one of the best insulators that exist. Finally, it has a higher hole mobility, which allows the fabrication of high speed P-channel field effect transistors.

Safety

Since arsenic is a part of this compound, it is considered very toxic and potentially carcinogenic. However, because the crystal is so stable, the body may only negligibly absorb ingested pieces. However, should the crystals be ground up into a fine powder, the body might be able to absorb the arsenic. California lists gallium arsenide as a carcinogen.