Properties
The optical and mechanical properties of InGaAs can be varied by changing the ratio of In and Ga, InxGa1-xAs. The InGaAs device is normally grown on an indium phosphide (InP) substrate. In order to match the lattice constant of InP and avoid mechanical strain, In0.53Ga0.47As, this composition has a cut-off wavelength of 1.68 μm.
By increasing the ratio of In further compared to Ga it is possible to extend the cut-off wavelength up to about 2.6 µm. In that case special measures have to be taken to avoid mechanical strain from differences in lattice constants.
GaAs is lattice mismatched to Ge by 0.08%. With the addition of 1.5% In to the alloy, InGaAs, becomes perfectly latticed matched to Ge. The complete elimination of film stress reduces the defect densities of the epi InGaAs layer compared to straight GaAs.
Read more about this topic: Indium Gallium Arsenide
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