IN-SITU STUDIES OF EPITAXIAL SILICON GROWTH BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

The value of in situ monitoring to study growth dynamics and surface r eaction kinetics in a gas source molecular beam epitaxy process is ill ustrated with reference to the growth of Si films on Si(001) substrate s using a beam of disilane (Si2H6). By using a combination of reflecti on high-energy electron diffraction (RHEED) and reflection anisotropy spectroscopy (RAS), we show first how morphological (long-range order) and local electronic structure effects can be separated in the evalua tion of growth dynamics. This involves the measurement of step density changes by RHEED concomitantly with the variation in domain coverage on the Si(001) (2 x 1)+(1 x 2) reconstructed surface by RAS. This appr oach is then extended to investigate the kinetics of hydrogen desorpti on, which is the rate-limiting step in Si growth from Si2H6. It is sho wn that over a significant temperature range, zeroth-order kinetics ar e obeyed and this is explained on the basis of a step-mediated desorpt ion process. Finally we show how this influences the growth rate on su bstrates of differing degrees of vicinality. (C) 1997 John Wiley & Son s, Ltd.