AlGaAs

Aluminum gallium arsenide, or AlxGa1-xAs, is a ternary III-V semiconductor alloy formed from aluminum arsenide (AlAs) and gallium arsenide (GaAs). The aluminum fraction x, which ranges from 0 to 1, allows the material’s electronic and optical properties to be tuned for specific applications. AlGaAs is most commonly used in combination with GaAs to create high-bandgap barriers and cladding layers in optoelectronic devices.

The bandgap of AlGaAs increases with increasing aluminum content. At room temperature, GaAs (x = 0) has a bandgap of about 1.42 eV, while higher aluminum content widens the bandgap toward that of AlAs (x ≈ 1). This tunability enables precise engineering of heterostructures such as quantum wells, separate-confinement heterostructure lasers, and waveguides. The lattice constant of AlGaAs varies only modestly with composition, which allows good lattice matching to GaAs substrates for many compositions, although deliberate strain can be used to tailor device performance.

Growth and fabrication are typically performed by molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). AlGaAs is frequently paired with GaAs to form heterojunctions and quantum wells used in laser diodes and light-emitting devices. In devices with higher aluminum content, selective oxidation of Al-containing layers can form AlOx, providing oxide-based current and optical confinement, a technique common in oxide-confined vertical-cavity surface-emitting lasers (VCSELs).

Common applications include GaAs-based laser diodes, LEDs, photodetectors, and as a wide-bandgap cladding or window layer in solar cells.