TEM STUDY OF THE STRUCTURE OF GAAS ON VICINAL SI(001) SURFACE GROWN BY MBE

Molecular beam epitaxy (MBE) grown GaAs films on Si substrates (001) 4 degrees off towards [111] A and towards [111] B, were examined by mea ns of transmission electron microscopy (TEM). The results indicate tha t in both samples, threading dislocations in the GaAs epilayer are blo cked mainly in a thin layer near the GaAs-Si interface. This thin laye r is like an inner interface, consisting of pyramidal islands and is f latter on the As growth surface than that on the Ga growth surface. In the type B sample, the density of dislocations is lower, the inner in terface is flatter and the number of twins is much larger than that in the type A sample.