  The reported diffusion constants for hydrogen in silicon vary over six orders
of magnitude. This spread in measured values is caused by the different
concentrations of defects in the silicon that has been studied. Hydrogen
diffusion is slowed down as it interacts with impurities. By changing the
material properties such as the crystallinity, doping type and impurity
concentrations, the diffusivity of hydrogen can be changed by several orders of
magnitude. In this study the influence of the hydrogen concentration on the
temperature dependence of the diffusion in high energy proton implanted silicon
is investigated. We show that the Arrhenius parameters, which describe this
temperature dependence decrease with increasing hydrogen concentration. We
propose a model where the relevant defects that mediate hydrogen diffusion
become saturated with hydrogen at high concentrations. When the defects that
provide hydrogen with the lowest energy positions in the lattice are saturated,
hydrogen resides at energetically less favorable positions and this increases
the diffusion of hydrogen through the crystal. Furthermore, we present a survey
of different studies on the diffusion of hydrogen. We observed a correlation of
the Arrhenius parameters calculated in those studies, leading to a modification
of the Arrhenius equation for the diffusion of hydrogen in silicon.
