On the Transient Negative Photoconductance in <italic>n</italic>-type Czochralski Silicon

Abstract

A transient negative photoconductance phenomenon is observed in n -type Czochralski silicon wafers. After a pulsed light excitation, the measured photoconductance drops to negative values and then increases to the original zero. The paper details how transient negative photoconductance is predicted by the Shockley–Read–Hall rate equations for a system of two defects. For this to occur, one defect must act as a majority carrier trap, and the other must be a relatively faster recombination channel. The specific conditions of these defects for a negative photoconductance to occur are derived analytically. Numerical modeling of this system shows good agreement with the experimental results. Finally, a method to extract the trap parameters from negative photoconductance for a sample with temperature-independent capture cross sections is demonstrated.