Strain-dependent morphology of spontaneous lateral composition modulations in AlAsm(InAs)n short-period superlattices grown by molecular beam epitaxy

The nature of spontaneous lateral composition modulation and its relationship to surface morphology during the growth of (AlAs)(m)(InAs)(n) short-period superlattices by molecular beam epitaxy are investigated as a function of the global strain between the short-period superlattice and (001)InP substrate. For samples grown under tension, transmission electron and atomic force microscopy reveal composition modulations along directions close to [310] coupled to a surface cusping. For samples grown under compression, we observe composition modulations roughly along the elastically soft [100] directions coupled to a surface rippling. For high strains with individual InAs layer thicknesses less than or equal to 1.6 monolayers, we observe weak or no composition modulations. (C) 1998 American Institute of Physics. [S0003-6951(98)00939-5].