Correlated SiGe wires shaped by regular step bunches on miscut Si(113) substrates

Highly regular step bunches have been observed in appropriately strained Si Ge/Si multilayers on miscut Si(113) substrates. Owing to the strong step-bu nching properties on the Si(113) surface, both the Si layers and the SiGe l ayers of the multilayers exhibit a regular pattern of large steps. Consider able SiGe material in the SiGe layers accumulates at the edges of the under lying large Si steps (step bunches), forming well-shaped SiGe wires. The Si Ge wires in the multilayers manifest an oblique correlation. A bending to v ertical correlation is observed when the built-in strain in the multilayers is large enough. The oblique correlation is well described in a thermodyna mic model of multilayer growth, based on the calculations of the in-plane s train fields of underlying step-modulated SiGe layers on the free surfaces of Si layers during growth. Si step bunches energetically form in the regio ns of maximum strain above the SiGe wires and cause lateral agglomeration o f SiGe material at Si step edges, resulting in the oblique correlation. The bending to vertical correlation occurs, in contrast, if the in-plane strai n field becomes large enough to cause the SiGe material to accumulate direc tly in the regions of maximum strain. [S0163-1829(99)04139-9].