THREADING DISLOCATION REDUCTION IN GAAS ON SI WITH A SINGLE INGAAS INTERMEDIATE LAYER

The threading dislocation reduction behavior upon insertion of a singl e thick InGaAs intermediate layer into the GaAs heteroepitaxial layers on Si has been investigated. In the X-ray diffraction, with increasin g InGaAs thickness below 0.5 mu m, the full width at half-maximum (FWH M) of the GaAs overlayer decreases even if the InGaAs thickness is bey ond the critical layer thickness. In the cross-sectional transmission electron microscopy (TEM) observations, it has been found that suffici ent misfit dislocations are introduced and that the threading dislocat ion density decreases at the GaAs/InGaAs interfaces in samples with In GaAs thicker than 0.1 mu m. The analysis based on the mechanical equil ibrium theory shows that misfit dislocation formation at the interface s plays an important role in reducing the threading dislocation densit y. The InGaAs intermediate layer is required to be thick enough to for m misfit dislocations at the interfaces with relaxation of strain in t he intermediate layer.