GaAs

GaAs, or gallium arsenide, is a compound semiconductor formed by gallium and arsenic. It is a III-V semiconductor with a direct bandgap of about 1.43 eV at room temperature, which makes it efficient at emitting light. The material crystallizes in the zinc blende structure, with a lattice constant of approximately 5.653 angstroms. GaAs exhibits high electron mobility and a high saturation velocity, contributing to fast electronic and optoelectronic performance. Its direct bandgap enables efficient light emission at near-infrared wavelengths, around 0.87 micrometers.

Growth and engineering of GaAs rely on epitaxial techniques, including molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), as well as liquid phase epitaxy in some cases. GaAs is commonly combined with aluminum, indium, or gallium to form ternary or quaternary alloys such as AlGaAs or InGaAs. These alloys enable heterostructures and quantum wells that improve carrier confinement and device performance. GaAs-based devices often employ doped regions and are fabricated into high-speed transistors and integrated circuits, including HEMTs and MMICs, as well as optoelectronic components.

Applications span high-speed electronics and communications, optoelectronics, and photovoltaics. GaAs-based laser diodes and light-emitting diodes are central to fiber-optic communications and optical storage. Photodetectors and infrared sensors frequently use GaAs alloys. In space and specialized terrestrial solar cells, GaAs solar cells offer high efficiency and strong radiation tolerance, contributing to multi-junction photovoltaic systems. Handling requires care due to the toxicity of arsenic, and manufacturing involves stringent safety and environmental controls.

Historically, GaAs devices became commercially important in the late 20th century, underpinning rapid advances in fast electronics and optical communications.