In1xGaxAs

In1−xGaxAs, commonly written as In1−xGaxAs or InGaAs, is a family of III–V semiconductor alloys formed from indium arsenide (InAs) and gallium arsenide (GaAs). The composition is controlled by the parameter x, which ranges from 0 to 1, so the material spans from GaAs (x = 0) to InAs (x = 1). The alloy inherits properties from both binaries and exhibits a continuously tunable bandgap and lattice constant.

The electronic structure of In1−xGaxAs is characterized by a direct bandgap for most compositions used in devices. The bandgap energy Eg(x) decreases with increasing indium content, roughly transitioning from Eg ≈ 1.43 eV for GaAs to Eg ≈ 0.36 eV for InAs, with a bowing parameter that makes the dependence nonlinear (typical bowing around 0.4–0.5 eV). At room temperature, a common lattice-matched composition to InP is x ≈ 0.53 (In0.47Ga0.53As), which yields a bandgap near 0.75 eV and a lattice constant close to that of InP. The lattice constant can be approximated by Vegard’s law as a ≈ (1−x)a(InAs) + x a(GaAs), giving about 5.86–5.87 Å for many device-relevant compositions.

Growth and fabrication of In1−xGaxAs are typically accomplished by molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). Common substrates include InP and GaAs, with lattice-matched or metamorphic buffer approaches used to access the 1.3–1.55 μm telecommunication window. Doping and heterostructuring enable high-speed electronics and optoelectronics.

Applications of In1−xGaxAs span infrared photodetectors, laser diodes, modulators, and integrated optoelectronic devices in telecommunications and sensing, leveraging its tunable bandgap and strong carrier mobility.