Threading Dislocation Reduction in GaAs on Si with a Single InGaAs Intermediate Layer

The threading dislocation reduction behavior upon insertion of a single thick InGaAs intermediate layer into the GaAs heteroepitaxial layers on Si has been investigated. In the X-ray diffraction, with increasing InGaAs thickness below 0.5 µ m, the full width at half-maximum (FWHM) of the GaAs overlayer decreases even if the InGaAs thickness is beyond the critical layer thickness. In the cross-sectional transmission electron microscopy (TEM) observations, it has been found that sufficient misfit dislocations are introduced and that the threading dislocation density decreases at the GaAs/InGaAs interfaces in samples with InGaAs thicker than 0.1 µ m. The analysis based on the mechanical equilibrium theory shows that misfit dislocation formation at the interfaces plays an important role in reducing the threading dislocation density. The InGaAs intermediate layer is required to be thick enough to form misfit dislocations at the interfaces with relaxation of strain in the intermediate layer.