A TEM study of Ge-on-(111)Si structures for potential use in high performance PMOS device technology

We have performed a transmission electron microscopical study of samples where pure Ge has been grown on differently oriented Si wafers by reduced pressure chemical vapour deposition. In the present study we examine pure Ge layers grown on (111)Si wafers by annular dark-field (ADF) scanning transmission electron microscopy (STEM) and by high-resolution electron microscopy (HREM). There is evidence of immediate strain relaxation taking place by dislocations and twinning. A novel configuration of micro-twins has been observed at the interface between the pure Ge and the underlying (111)Si wafer. Growth mechanisms and models to explain the interfacial configurations of this type of wafer are suggested.