INCREASE OF OVERLAYER CRITICAL THICKNESS BY OFF-ANGLED SUBSTRATES

Molecular beam epitaxial (MBE) grown InAs layers on off-angled GaAs substrates are experimentally investigated by transmission electron microscopy (TEM), and the critical thickness of the lattice-mismatched grown layers on the off-angled substrates are theoretically discussed based on calculations using the valence-force field method. Dislocation densities observed by TEM in the InAs layers grown on the just-oriented and the off-angled GaAs substrates are compared with each other. In the 4 ML grown InAs layer on a 3.5 degrees off-angled substrate, no dislocations are observed. On the other hand, a high density of dislocations is observed in the 4 ML grown InAs layer on the just-oriented substrate. This result indicates that the off-angle of the substrate changes the critical thickness. The theoretical calculation interprets the increase of the overlayer critical thickness on the off-angled substrate.