InGaAs

Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide) is a ternary alloy (chemical compound) of indium, gallium and arsenic. Indium and gallium are both from boron group (group III) of elements while arsenic is a pnictogen (group V) element. Thus alloys made of these chemical groups are referred to as "III-V" compounds. Because they are from the same group, indium and gallium have similar roles in chemical bonding. InGaAs is regarded as an alloy of gallium arsenide and indium arsenide with properties intermediate between the two depending on the proportion of gallium to indium. InGaAs is a semiconductor with applications in electronics and optoelectronics.

Indium gallium arsenide is a popular designation for gallium-indium arsenide (GaInAs). InGaAs is a direct bandgap, pseudo-binary alloy composed of two III-V semiconducting materials: (GaAs)_X and (InAs)_1−X. The alloy is miscible over the entire compositional range from GaAs (bandgap = 1.42 eV at 300 K) to InAs (bandgap = 0.34 eV at 300 K).

According to IUPAC standards the preferred nomenclature for the alloy is In1-XGaXAs where the group-III elements appear in order of increasing atomic number, as in the related alloy system AlXGa1-XAs.

InGaAs has a lattice parameter that increases linearly with the concentration of InAs in the alloy. The liquid-solid phase diagram shows that during solidification from a solution containing GaAs and InAs, GaAs is taken up at a much higher rate than InAs, depleting the solution of GaAs. During growth from solution, the composition of first material to solidify is rich in GaAs while the last material to solidify is richer in InAs. This feature has been exploited to produce ingots of InGaAs with graded composition along the length of the ingot. However, the strain introduced by the changing lattice constant causes the ingot to be polycrystalline and limits the characterization to a few parameters, with uncertainty due to the continuous compositional grading in the materials.

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