AlInGaP

AlInGaP, short for aluminum-indium-gallium phosphide, is a quaternary III–V semiconductor alloy used primarily for visible light emitters. It combines aluminum, indium, gallium and phosphorus in a single crystal lattice and is typically grown on GaAs or GaP substrates using epitaxial techniques such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The composition is adjusted to tune the lattice constant and the direct bandgap of the material, enabling emission in the red to yellow portion of the visible spectrum.

The emission wavelength of AlInGaP devices is controlled by the relative amounts of Al, In, and Ga. Increasing aluminum content generally widens the bandgap and shifts emission toward shorter wavelengths, while indium lowers the bandgap and pushes emission toward longer wavelengths within the red to orange range. Practical devices are often realized as multiple quantum well structures within a p–n junction, with p-type and n-type doped cladding and contact layers to improve performance and efficiency.

Applications for AlInGaP devices include high-brightness red, orange, and yellow light-emitting diodes and laser diodes, which are used in displays, signage, automotive lighting, and optical data storage components. While blue and green visible light sources are primarily based on other material systems (such as GaN or GaP), AlInGaP remains a key technology for red and orange emission in GaAs-based optoelectronics.

Advantages of AlInGaP include good color purity and compatibility with well-established GaAs device processing. Limitations include a relatively narrow tunable range compared to other systems and sensitivity to composition control to achieve uniform emission.