CORRELATED ROUGHNESS IN (GE(M)/SI(N))P SUPERLATTICES ON SI(100)

We have used high-resolution x-ray reflectivity to determine the interface microstructure in a (Ge(m)/Si(n))p superlattice grown at 350-degrees-C. In-plane correlation of roughness is observed, causing a distinct splitting of superlattice peaks in transverse rocking scans. Different interfaces are not independent, but rather the terrace structure of the substrate is identically replicated, forming a superlattice with vertically correlated (conformal) interface roughness. This is a result of limited lateral migration of deposited Si and Ge atoms during the low-temperature growth process.