Gallium arsenide

|----- ! colspan=" 2" bgcolor=" #FFDEAD" | Structure |----- | Constant of mesh || : 0.56533 Nm |----- | Crystalline structure || cubic centered face, type Sphalerite |----- ! colspan=" 2" bgcolor=" #FFDEAD" | Electronics |----- | Energy band to 300 K || : 1.424 eV |----- | Effective mass of the electron || : 0.067 m _e |----- | Effective mass of the light hole || 0,082 m _e |----- | Effective mass of the heavy hole || 0,45 m _e |----- | Electronic mobility to 300 K || : 9200 cm ²/(V·S) |----- | Mobility of the holes to 300 K || 400 cm ²/(V·S) |----

The gallium arsenide ( GaAs ) is a chemical Composé of Arsenic and Gallium.

It is a material Semi-conducteur used in particular to carry out components Micro-onde S and components Opto-électronique S, electroluminescent diodes Infrarouge or photovoltaic cells. GaAs is a semiconductor known as “ III-V ” because the Gallium and the Arsenic respectively present 3 and 5 electrons of valence.

Crystalline structure

The gallium arsenide has a crystalline structure of " type; Sphalerite ". If it is considered that the gallium atoms follow a structure of the type Cubique centered face, the arsenic atoms occupy as for them 4 of the 8 tetrahedral sites of this mesh (and vice versa).

Comparisons GaAs-Silicon

Assets of gallium arsenide

The gallium arsenide has some electric properties higher than those of the Silicium:

It has more an high speed of saturation of the electrons, and those have a larger mobility, which enables him to function at frequencies higher than 250 Ghz.
the devices with GaAs technology generate less noise in high frequencies than those containing silicon.
They can in the same way function with power higher, because of a higher tension of breakdown.

These properties make gallium arsenide a compound of choice, in particular in the manufacture of circuits for cellphones, satellite communications, technology microwave, like certain devices with radar. The gallium arsenide is also used in the manufacture of Diode Gunn.

Another asset of gallium arsenide is its gap direct (contrary to silicon which has to him an indirect gap) what enables him to emit light (silicon emits very little light, even if recent technological advances made it possible to use it to make LEDs or Laser S).

The properties of gallium arsenide, in particular its commutation rate, one makes appear like an ideal material, in particular for applications in data processing. In the Eighties, much thought that the market of micro-electronics would be dominated in the long term by gallium arsenide, thus replacing silicon. The first attempt at evolution is due to the salesmen of Superordinateur S CRAY Research, Convex, and Combining. CRAY developed a machine containing gallium arsenide, the CRAY-3, but the financial efforts of research were insufficient, and the company went bankrupt in 1995.

Assets of silicon

Silicon has three main advantages with respect to gallium arsenide.

First of all it is particularly abundant (the most abundant element on Earth after the Oxygène). More robust, it makes it possible to make larger wafers (~300mm compared with ~150mm for gallium arsenide).

The second advantage of silicon is the existence of one as of its oxide, the dioxide of silicon (SiO₂), undoubtedly one of best insulators existing. This insulator can be easily built-in with the silicon circuits, and these insulating layers adheres well to the layers of If. The gallium arsenide does not form to him not a stable insulating layer which adheres correctly.

The third is undoubtedly most important. The mobility of the hole S in silicon is higher by far has that of gallium arsenide. This great mobility allows the manufacture of field-effect transistors - channel P with great speed, necessary in technology CMOS. From this lack, the gallium arsenide forever which been able to be really competitive with respect to silicon.

See too

Trimethylgallium
Phospho-arsenide of gallium
Arsenide of gallium-aluminum
Card of data of safety

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