Hydrogen desorption kinetics from silicon-germanium alloy surfaces

Silicon alloy growth kinetics at low temperature parallels the desorption kinetics of hydrogen. Growth rates increase in a nonlinear fashion with germanium content and hydrogen desorption is enhanced as germanium content in the film increases. This paper examines a model to explain the effect of germanium on hydrogen desorption kinetics that accounts for the enhanced desorption rate by the migration of hydrogen from silicon surface sites to germanium sites, where essentially all the hydrogen desorbs. Ion scattering spectroscopy is used to establish the surface composition, and nonlinear parameter estimation techniques are used to model the temperature programmed desorption spectra and extract the kinetic parameters. The paper shows the desorption kinetics are related directly to the surface composition and the kinetic competition between sites for desorption.