Note on Quenching of Photoconductivity in Cadmium Sulfide

The spectral distribution of quenching of the photoconductivity in cadmium sulfide crystals has been investigated. The process is interpreted as excitation of trapped holes by the quenching radiation, followed by thermal ionization to the filled band. Freeing of trapped electrons does not appear important. Two peaks in the quenching spectrum occur at hν=1.5 and 0.9 ev and are attributed to different hole traps. Transient changes in photoconductivity on application or removal of radiation in the red are shown to arise from simultaneous excitation and quenching processes with different time dependences. As a consequence, the quenching spectrum can be followed for some distance into the excitation region and vice versa.