In situ Ellipsometric Measurement during Growth of Ge on Si(111) by Molecular Beam Epitaxy

Abstract

Ellipsometric measurements were applied to investigate Ge heteroepitaxial growth by molecular beam epitaxy on a Si(111) substrate, and the changes of optical constants and film thickness were monitored. Reflection high-energy electron diffraction (RHEED) patterns and atomic force microscopy (AFM) images were also observed. Remarkable changes of optical constants were observed during the film growth depending on the change of surface morphology due to the Stranski–Krastanov (S–K) growth mode of Ge films on Si(111). When Ge was grown further, the RHEED pattern showed the characteristic reconstruction surface of Ge(111) in spite of the Ge heteroepitaxial growth on Si(111) substrate. The change of optical constants during the film growth could be well explained in terms of the S–K growth mode and coalescence of islands. It is shown that in situ ellipsometry is a useful method for investigating the growth mode as well as monitoring the film thickness.