Gallium arsenide

Gallium arsenide (GaAs) is a compound semiconductor made from gallium and arsenic. Its direct band gap and high electron mobility suit it to optoelectronics and high-frequency devices.

Direct band gap: An electronic band gap in which a conduction-band minimum and valence-band maximum occur at the same crystal momentum. This alignment lets GaAs emit and absorb light efficiently without a momentum-changing phonon.
Light-emitting diode: A semiconductor device that emits light when electrical current flows through it. GaAs-based alloys provide efficient infrared emission in LEDs.
Zinc blende structure: A cubic crystal structure in which two interpenetrating face-centered cubic sublattices are offset by one quarter of a body diagonal. GaAs crystallizes in this structure, with gallium and arsenic occupying separate sublattices.
Silicon: A chemical element with atomic number 14 that is the dominant semiconductor material in integrated circuits. Silicon is cheaper and forms a strong native oxide, while GaAs offers higher electron mobility and direct-gap optics.
Electron mobility: A measure of how quickly electrons drift through a material under an applied electric field. High electron mobility helps GaAs transistors operate at high frequencies.
Laser diode: A semiconductor laser that generates coherent light through stimulated emission in an electrically driven junction. Direct-gap GaAs compounds are widely used in near-infrared laser diodes.
Gallium: A soft, silvery chemical element with atomic number 31. Gallium supplies the group-III constituent in the GaAs lattice.
Indium phosphide: A compound semiconductor of indium and phosphorus used in high-speed and optoelectronic devices. InP competes with GaAs in fast electronics and optical communications, with different band and substrate properties.
Band gap: The energy range between a solid's valence and conduction bands that contains no allowed electronic states. GaAs's band gap sets the photon energies its devices can emit or detect.
High-electron-mobility transistor: A field-effect transistor that uses a high-mobility carrier channel, often formed at a semiconductor heterojunction. GaAs heterostructures enable fast, low-noise transistors for microwave circuits.

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