POSTGROWTH THERMAL ANNEALING OF GAAS ON SI(001) GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY

GaAs epitaxial layers, 0.375 to 3.75 mum in thickness. were grown on vicinal Si(001), with and without post-growth thermal annealing. These layers were studied by double crystal X-ray diffraction; it was shown that for these samples the (004) rocking curve widths were dominated by the threading dislocation densities. The observed (004) rocking curve widths were then used to determine the threading dislocation densities. It was found that post-growth annealing is effective in reducing the threading dislocation density of epitaxial GaAs on vicinal Si(001). There is a minimum achievable dislocation density which is independent of the annealing temperature. This density is inversely proportional to the film thickness. as is predicted by a half-loop theory for the annihilation of dislocations by annealing. The rate at which dislocations are removed from 1.5 mum thick GaAs on Si by annealing is thermally activated (E(a) = 1.91 eV) and is not affected by the presence of thermal strain.