Charge collection in silicon $p^+$–$n$–$n^+$-structures at temperature 40 mK

Charge collection in 1 mm thick Si $p^+$–$n$–$n^+$-structures in the range of electric field up to $\sim$ 7.5 kV/cm is studied at a temperature 40 mK, which is the target temperature for the operation of Si bolometric antineutrino detectors. Analysis of the structure current responses shows that under these conditions the silicon bulk is transformed into an electrically neutral insulator with a trapping time of nonequilibrium electrons of $\sim$ 370 ns and holes of more than 1 $\mu$s. Charge collection demonstrates two stages: a space charge limited current and a drift of a thin carrier package with kinetics controlled by the collected charge magnitude. Calculations of the change in the electric field accompanying the drift are presented and a decrease in the carrier collection time to 10 ns is shown.