Which Surfactant Shall We Choose for the Heteroepitaxy of Ge/Si(001)? –Bi as a Surfactant with Small Self-Incorporation–

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Abstract
While the effectiveness of surfactants in Si/Ge heteroepitaxial growth has recently been reported, their disadvantages of self-incorporation and poor surface morphology restrict their practical application. We propose Bi as a surfactant which overcomes these disadvantages. We demonstrate by means of reflection high-energy electron diffraction and secondary ion mass spectrometry (SIMS) that Bi is an effective surfactant for Si/Ge heteroepitaxy in preventing both 3D islanding and surface segregation of Ge, while the amount of Bi incorporated in the epitaxial layer is smaller than the detection limit of the SIMS instrument (16 cm-3) and Bi can be removed easily by desorption at temperatures as low as 575°C.