SURFACE-ROUGHNESS, STRAIN, AND ALLOY SEGREGATION IN LATTICE-MATCHED HETEROEPITAXY

Spinodal decomposition of ternary semiconductor alloys during lattice- matched heteroepitaxy is considered here. It has been previously demon strated that a perfectly flat surface (with no step) would forbid allo y demixing. The case of a rough surface is the purpose of this article . How the possibility of a better strain relaxation introduced by the surface roughness can favor alloy demixing is analyzed first. The pres ent results are exemplified by the AlInAs lattice matched to the InP c ase. Second, a step-by-step model is proposed to simulate the growth p rocess on a rough surface. This model leads to a description of the st rain and alloy demixing during this growth. This study clearly shows h ow and why the atoms corresponding to binary materials with lower surf ace tension naturally tend to segregate towards bumped areas. (C) 1998 American Vacuum Society.