Gallium arsenide — properties, structure, and applications

Crystal structure and electronic character

GaAs crystallizes most commonly in the zincblende (cubic) structure, which provides a direct electronic bandgap. This direct bandgap makes GaAs efficient at emitting and absorbing light, distinguishing it from indirect-gap semiconductors such as silicon. The material also offers higher electron mobility than silicon, which improves performance at high frequencies. For background on the constituent elements, see gallium and arsenide.

Preparation and processing

Single crystals and epitaxial films of GaAs are commonly produced by techniques such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). These methods enable precise control of composition, doping and heterostructure formation (for example AlGaAs/GaAs layers). Doping with donors or acceptors tailors the electrical conductivity for specific device functions. See also materials described as ions in ionic/covalent compounds.

Uses and applications

• Optoelectronics: light-emitting diodes (LEDs), laser diodes and photodetectors benefit from GaAs's direct bandgap.
• High-frequency electronics: microwave and millimeter-wave integrated circuits, radar and satellite transceivers exploit its high electron mobility.
• Solar cells: space-grade photovoltaic cells often use GaAs because of its radiation resistance and high efficiency.
• Research devices: heterostructures, quantum wells and high-electron-mobility transistors (HEMTs) are built using GaAs or related alloys.

Safety and notable facts

Arsenic compounds can be toxic, so synthesis and processing of GaAs require appropriate controls to limit exposure and environmental release. The material is also a foundation for many compound-semiconductor technologies and is often alloyed (for example with aluminum or indium) to tune electronic and optical properties. For more technical details on oxidation states and bonding, consult sources about the oxidation state of gallium in compounds.

Because of its combination of optical and electronic properties, GaAs remains important for specialized applications where performance at high frequency, high efficiency in light emission or resilience in space environments outweighs its higher cost relative to silicon.