CONCENTRATION-DEPENDENCE OF GE SEGREGATION DURING THE GROWTH OF A SIGE BURIED LAYER

X-ray photoelectron spectroscopy (XPS) measurements of a series of films with varying x and cap thicknesses were made to determine the Ge profile in both thin Si cap layers and the Si1-xGex buried layers grown at 500-degrees-C. The inelastic mean free path of 267 eV electrons through a silicon overlayer was measured to be 1.2 nm. The Ge profile was inferred by simulating the surface segregation process using a two-state exchange mechanism, and comparing the expected XPS spectra to the obtained data. The resulting model predicts a floating surface layer rich in Ge during the growth of the Si1-xGex layer and the Si cap that results in distortion of both interfaces of the buried layer. The interface formed upon beginning the growth of the buried Si1-xGex layer can be wide, and estimates of the width of the ''leading'' interface range from approximately 20 monolayers (MLs) for an x = 0.05 layer, and approximately 10 MLs for an x = 0.1 layer grown at 500-degrees-C.