Correlated roughness in (Gem/Sin)p superlattices on Si(100)

Abstract

We have used high-resolution x-ray reflectivity to determine the interface microstructure in a (${\mathrm{Ge}}_{\mathit{m}}$/${\mathrm{Si}}_{\mathit{n}}$ ${)}_{\mathit{p}}$ superlattice grown at 350 °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.