Reduction of threading dislocations in GaAs on Si by the use of intermediate GaAs buffer layers prepared under high V–III ratios

Abstract

We have shown that the insertion of a GaAs layer prepared by organometallic vapor phase epitaxy under very high (VH) V–III ratios into a GaAs/Si epitaxial structure improves its crystallinity after thermal cycle annealing (TCA). The PL intensity of the upper GaAs epilayer with the VH-V/III GaAs intermediate buffer layer is found to be larger than that with a normal GaAs layer. It is also observed in cross-sectional TEM that the number of through dislocations is smaller for the sample with this novel buffer layer and most threading dislocations are confined to below the buffer layer after TCA, which is in good agreement with the PL result. We tentatively attribute the origin of this improvement of the GaAs/Si epilayer to an increased concentration of Ga vacancies which will migrate and relieve the tensile stress.