AlxGa1xAs

AlxGa1-xAs is a ternary III-V semiconductor alloy formed by incorporating aluminum into gallium arsenide. The composition is indicated by x, the fractional aluminum content, with x ranging from 0 to 1. The material crystallizes in the zinc blende structure and is typically grown on GaAs substrates to form heterostructures and quantum wells. The lattice constant increases slightly with aluminum content, which allows strain engineering in layered devices.

The bandgap of AlxGa1-xAs at room temperature increases with x, ranging from about 1.42 eV for GaAs (x = 0) to about 2.16 eV for AlAs (x = 1). The alloy is direct-bandgap for small aluminum content (approximately x < 0.4) and tends toward an indirect bandgap at higher aluminum content, which reduces light-emission efficiency in that regime. The refractive index decreases as the bandgap widens, a property exploited in optical confinement.

Growth and doping are commonly performed by molecular beam epitaxy or metal-organic chemical vapor deposition. Doping with donors such as silicon yields n-type material, while acceptors such as beryllium produce p-type material, enabling the formation of p–n junctions and electronic devices.

Applications include its use as a high-bandgap barrier or cladding layer in GaAs-based optoelectronic devices, where it provides carrier confinement in quantum wells and waveguides. AlxGa1-xAs is widely employed in laser diodes, light-emitting diodes, and photodetectors, often in combination with GaAs wells, and is a standard material in monolithic GaAs/AlGaAs optoelectronic structures.