InGaAsP

InGaAsP, or indium gallium arsenide phosphide, is a quaternary III–V semiconductor alloy used primarily in optoelectronic devices on indium phosphide (InP) substrates. It is formed by adjusting the relative amounts of indium (In), gallium (Ga), arsenic (As), and phosphorus (P) to produce a material with a tunable band gap and lattice constant. The composition is commonly written as In1−xGaxAsyP1−y, and for a given InP substrate, y is chosen to achieve lattice matching, minimizing strain and dislocations.

By varying x and y, the material covers a band gap roughly from the near-infrared to the mid-infrared, enabling emission or detection in wavelengths around 1.3 and 1.55 micrometers, which are important for optical fiber communications. The quaternary system allows efficient direct-bandgap operation, making InGaAsP suitable for laser diodes, light-emitting diodes, and photodetectors, often used in telecom and integrated photonics.

Growth is typically performed by epitaxial techniques such as metal-organic chemical vapor deposition (MOCVD or MOVPE) or molecular beam epitaxy (MBE) on InP substrates. The ability to form quantum wells and multi-layer heterostructures enables high-performance devices with tailored optical and electronic properties. Doping with n- or p-type dopants enables standard diode and laser structures, including separate-confinement heterostructure lasers and active-region quantum-well devices.