Another advantage of GaAs is that it has a direct bandgap. This means that it can be used to emit light. Silicon has an indirect bandgap, and so is very poor at emitting light. Nonetheless, recent advances may make silicon LEDs and lasers possible. Silicon has two major advantages over GaAs. First, silicon is cheap. This is for several reasons: silicon's large wafer size (maximum of ~300mm compared to ~150mm diameter), high strength allowing for easier processing, and of course the scale of the economy.

The second major advantage is the existence of silicon dioxide—one of the best known insulators of any kind. Silicon dioxide can easily be incorporated into silicon circuits wherever a good insulator is required. GaAs circuits must eithe

Gallium arsenide is used in the manufacture of light-emitting diodes (LEDs), which are found in optical communications and control systems. Gallium arsenide can replace silicon in the manufacture of linear and digital ICs. Digital devices are used for electronic switching, and also in computer systems.

Typical specifications for surface quality in the infrared are 40-20 or 60-40 scratch dig in the 2 to 7µm spectral region and 60-40, 80-50 or 120-80 scratch-dig for the 7-15µm area, depending upon system performance requirements. In the infrared, typical surface figure ranges from 1/2 wave to 2 waves @0.6328 µm depending on the system performance requirements. Available coatings for GaAs include a BBAR for 3 to 5µm spectral region, and a BBAR for the 8 to 12µm spectral region. Many other specialized bands are possible within the 2 to 15µm spectral region.

Because of the lower power consumption of gallium arsenide MOSFETs, the talk time for cellular phones would be extended. Meanwhile, wireless base stations would be more powerful and more efficient. Because of design limitations, it's more likely that gallium arsenide MOSFETs first would be used in wireless applications, as opposed to computer applications, such as microprocessors. That's because only a few thousand transistors are needed for a cellular phone chip, compared to tens of thousands in microprocessors.

Some topics in this essay:
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