  Extensive irradiation of silicon crystal sensors by high energy particles in
e. g. accelerators yield defect clusters of different types. Trapping of
electrons and holes result in extended internal electric fields that drive
remaining free charges. The question whether these internal electric fields
affect the experimental observables, e.g. recombination process and lifetime of
free charges is the main focus of this paper. Including the drift and diffusion
of electrons and holes we calculate the recombination rate in a cubic sample
with a single dipolar cluster of defects. It is shown that the large effect on
charge lifetime is to be expected when charge diffusion length during the
charge lifetime is comparable to the dimensions of the cluster. If the
diffusion length exceeds the cluster size, the cluster barely affects the
recombination rate.
