Abrupt Si/Ge/Si(001) interfaces fabricated with Bi as a surfactant

Fabrication of atomically abrupt Si/Ge/Si heterointerfaces was demonstrated using Bi as a surfactant. Cross-sectional high-resolution transmission electron microscopy shows that the surfactant improves the abruptness at the Si/Ge/Si heterointerface through the suppression of Ge surface segregation. The existence of distinct atomic steps at the heterointerfaces indicates that the flatness at the heterointerfaces is degraded by the surfactant due to the suppression of surface migration. A growth procedure to fabricate abrupt and flat Si/Ge/Si interfaces by alternating adsorption and desorption of Bi atoms is proposed.