Persistent photoconductivity in silicon wafers

Persistent photoconductivity effect in silicon wafers was observed using specifically designed test structures. Persistent changes in conductivity can reach 0.01% in wafers with a doping level of . The recovery time constant is in the range 10-30 min at room temperature. Oxygen-rich-Czochralski-grown wafers were compared with oxygen-poor float-zone-grown ones. The persistent photoconductivity is much higher in the Czochralski wafers. This indicates that this effect is most probably related to oxygen in silicon. To the best of our knowledge, such an effect has never been observed before in silicon crystals.