Relationship between the lateral length and thickness of the platelets in naturally occurring strained layer superlattice structures

The molecular beam epitaxial growth of InAs0.5Sb0.5 onto (001) surfaces bel ow 430 degreesC results in the formation of a "natural" strained layer supe rlattice (n-SLS). Transmission electron micrographs of [110] cross sections showed the existence of two different alloy compositions that formed a tet ragonally distorted interleaved platelet structure in which the interfaces were highly regular and ran approximately parallel to the growing surface. It is found that the structure of the n-SLS can be changed systematically b y carefully controlling the InAs0.5Sb0.5 growth conditions. A simple relati onship is derived relating the lateral size of the platelet to its thicknes s that is found to hold experimentally for n-SLS structures. It is suggeste d that the n-SLS structure occurs because it corresponds to the minimum fre e energy configuration of the growing crystal. A similar formalization has been applied to periodic modulations in other material systems. (C) 2000 Am erican Institute of Physics. [S0021-8979(00)08321-3].