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

Abstract

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 ∼200 Å of thermal oxide was exposed to gaseous molecular hydrogen at temperatures between 135 and 300 °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 “Pb” 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 H2.