Defect structures in MBE grown GaAs on Si

The major remaining limitation for the application of GaAs on Si is the reduction of high dislocation density and resulting electronic defects in the GaAs layer. We have investigated defect structures in GaAs layers grown on Si by molecular beam epitaxy (MBE) with different structures in the GaAs/Si interface region. Interface region variables include thickness, designs of In_xGa_1-xAs/GaAs strained layer superlattices(SLSs) and growth conditions of the GaAs buffer layers(As₄Ga ratio and in-situ annealing at 750°C). These layers were examined by transmission electron microscope(TEM) and double crystal X-ray diffraction. Defects, such as dislocations and stacking faults, exhibit a much stronger dependence on the growth conditions of the GaAs buffer layers compared to the magnitude of strain energy in the SLSs. Larger misorientation angles(0.35° and 0.26°) between the GaAs epilayers and Si substrates resulted in reduced defect densities compared to more highly dislocated layers with less misorientation(0°, 1.0°, 1.0° and 0.3°).