Growth of Ge layers on Si(100) monitored by in situ ellipsometry

Ellipsometric monitoring of the growth of Ge layers on Si(100) by pyrolysis of GeH 4 at substrate temperatures of 400, 450 and 500°C was performed by using a single wavelength ellipsometer based on the four detector photopolarimeter. By coupling ellipsometric monitoring with X-ray photoelectron spectroscopy surface analysis, the changeover between bi-dimensional and tri-dimensional growth modality at 450°C was found at Ge coverage of about 1 ML. The recorded ?-? data were analysed by using a growth model based on the Effective Medium Approximation (EMA) in order to derive the fraction of voids v and the thickness of the EMA layer h EMA. The values found for v were consistent with the clustered morphology observed by Atomic Force Microscopy (AFM) analysis of the samples. A qualitative model for the island evolution and for the growth rate of the equivalent Ge layer as a function of the substrate temperature was derived from the calculated v and h EMA, in agreement with the indications given by AFM and Rutherford backscattering spectroscopy film characterisation. © 1998 Elsevier Science S.A.