Paramagnetic Ge dangling bond type defects at (1 0 0)Si1−xGex/SiO2 interfaces (Invited Paper)

The work addresses the occurrence of Ge dangling bond type point defects at GexSi1−x/insulator interfaces as evidenced by conventional electron spin resonance (ESR) spectroscopy. Using multifrequency ESR, we report on the observation and characterization of a first nontrigonal Ge dangling bond (DB)-type interface defect in SiO2/(1 0 0)GexSi1−x/SiO2/(1 0 0)Si heterostructures (0.27 ⩽ x ⩽ 0.93) manufactured by the condensation technique, a selective oxidation method enabling Ge enrichment of a buried epitaxial Si-rich SiGe layer. The center, exhibiting monoclinic-I (C2v) symmetry is observed in highest densities of ∼7 × 1012 cm−2 of GexSi1−x/SiO2 interface for x ∼ 0.7, to disappear for x outside the ]0.45–0.87[ interval, with remarkably no copresence of Si Pb-type centers. Neither are trigonal Ge DB centers observed, enabling unequivocal spectral analysis. Initial study of the defect passivation under annealing in molecular H2 has been carried out. On the basis of all data the defect is depicted as a Ge Pb1-type center, i.e., distinct from a trigonal basic Ge Pb(0)-type center (Ge3Ge). The modalities of the defect’s occurrence as unique interface mismatch healing defect is discussed, which may widen our understanding of interfacial DB centers in general.