aInxAl1xAs

InxAl1−xAs, commonly written as InxAl1−xAs or InAlAs, is a ternary III–V semiconductor alloy consisting of indium arsenide (InAs), aluminum arsenide (AlAs), and arsenic. The composition is described by the mole fraction x of indium, with 0 ≤ x ≤ 1. The alloy is used in a range of optoelectronic and high-speed electronic devices, often in epitaxial heterostructures with other III–V materials.

Crystal structure and lattice parameters

InxAl1−xAs adopts the zinc blende crystal structure typical of many III–V semiconductors. The lattice constant varies roughly linearly with composition according to Vegard’s law, a(x) ≈ (1−x)a(AlAs) + x a(InAs), though a small bowing term may apply in some growth conditions. This tunability of the lattice parameter, along with the bandgap, enables a variety of heterostructures and strain states when grown on different substrates.

Electronic properties and bandgap

The alloy provides a tunable bandgap that broadens from the narrow-gap end of InAs (about 0.36 eV at room temperature) toward the wide-gap end of AlAs (about 2.16 eV). The exact bandgap value and whether the material is direct or indirect at room temperature depend on composition as well as strain from the substrate. InxAl1−xAs therefore offers flexible spectral control, spanning infrared to near-ultraviolet ranges in principle, subject to format and growth conditions.

Growth, substrates, and applications

InxAl1−xAs is grown by epitaxial techniques such as molecular beam epitaxy (MBE) or metal–organic chemical vapor deposition (MOCVD/MOVPE). It is commonly used as barrier or cladding material in GaAs- and GaInAs-based heterostructures, quantum wells, and photodetectors, as well as in high-speed electronic devices where precise bandgap and strain engineering are advantageous. Growth typically requires careful management of lattice mismatch and thermal expansion differences through buffering and substrate choice.