MODEL FOR HYDROGEN DESORPTION IN SIGE(100) FILMS

A model to describe hydrogen desorption from SiGe(100) that takes into account the nature of the surface bonding is presented. It is based o n the presence of three dimer types in the SiGe(100) surface (Si-Si, G e-Ge, and Si-Ge), in which there is a thermodynamic preference of hydr ogen atoms to pair up before the desorption reaction. The desorption k inetics are, therefore, assumed to be controlled by the population of paired hydrogens in the three dimer types, according to a first-order law. It is also assumed that diffusion, which tends to drive the occup ancy of hydrogen atoms in the dimers towards the thermodynamic equilib rium distribution, is not instantaneous. The comparison with experimen tal results shows that desorption is a diffusion limited process. (C) 1997 American Vacuum Society.