Rate constants for the reaction of H2 with defects at the SiO2/Si(111) interface

A radio frequency probe has been used to monitor changes in charge-carrier recombination centers at a SiO2/Si interface by following the steady-state photogenerated carrier concentration in the silicon. A silicon surface covered with similar to 200 Angstrom of thermal oxide was exposed to gaseous molecular hydrogen at temperatures between 135 and 300 degrees C. The reaction was found to occur with a nonexponential rate law that could be described by a cluster of rate constants governed by a Gaussian distribution of activation energies. At high temperatures, the dominant reaction was found to be that of "P-b" centers with a rate law that is consistent with that previously obtained by electron paramagnetic resonance. At low temperatures the reaction is dominated by the passivation of a carrier recombination center with a much lower activation energy. This new species makes up about 25% of the total recombination center concentration at the Si/SiO2 interface. Almost 20% of the recombination centers could not be passivated by H-2. (C) 2000 American Institute of Physics. [S0021-8979(00)03110-8].