InGaAs materials with InGaAs in the absorption layer and cut-off wavelength set at 1.7um (lattice-matched to InP) are often referred to as Standard, while materials with cut-off above 1.7um (lattice-mismatched) are called Extended.
Omitting the Phosphorus (y=1), to create the ternary InGaAs, would allow to lattice-match to InP at the composition of Indium at 53% – In(0.53)Ga(0.47)As – with energy band gap of 0.73eV equal to cut-off wavelength of around 1.7um.Ĭut-off wavelength means that only wavelengths shorter than the given value will be absorbed and any values above will have very low or none detectivity a parameter measured as D* (cm Hz^1/2W^-1) and describing a normalized signal-to-noise ratio of a device. The quaternary InGaAsP, which would be the result of mixing all four chemical elements, finds its usage in the 1.0-1.6um range, as relevant band-gaps will be achieved when lattice-matching InGaAsP to InP. The lattice constant is a key value to designing the epitaxial stack and predicting the strain that can occur in the layers. An adjustment of x in In(x)Ga(1-x)As allows to lower the energy band gap and therefore make the light spectral range longer, but this happens at the cost of changing the lattice constant and mismatching to an InP substrate. By the rule, as given by Planck equation E=hν, the higher the energy the higher the frequency, which is inversely proportional to the wavelength. In quaternary InGaAsP and ternary InGaAs a variety of x and y values are possible, and each combination will tune the semiconductor to different applications.Īdjusting the proportion of Indium to Gallium and Arsenic to Phosphorus affects the energy band-gap and lattice parameter of the compound. For binary GaAs, InP, GaP, or InAs, the x and y are set to 0 or 1. The InGaAs layer itself is a III-V semiconductor that belongs to the family of In(x)Ga(1-x)As(y)P(1-y). The so-called InGaAs material refers to a complete epitaxial stack composed of a variety of layers, with InGaAs forming the key part – the absorption – and being responsible for the material’s optical properties.
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