High quality Ge on Si by epitaxial necking

We show that pure Ge grown selectively on ${\mathrm{SiO}}_2/\mathrm{Si}$ substrates in 100 nm holes is highly perfect at the top surface compared to conventional Ge lattice-mismatched growth on planar Si substrates. This result is achieved through a combination of interferometric lithography ${\mathrm{SiO}}_2/\mathrm{Si}$ substrate patterning and ultrahigh vacuum chemical vapor deposition Ge selective epitaxial growth. This “epitaxial necking,” in which threading dislocations are blocked at oxide sidewalls, shows promise for dislocation filtering and the fabrication of low-defect density Ge on Si. Defects at the Ge film surface only arise at the merging of epitaxial lateral overgrowth fronts from neighboring holes. These results confirm that epitaxial necking can be used to reduce threading dislocation density in lattice-mismatched systems.