Fixed charge density in dielectrics deposited on c-Si using space charge region dominated lifetime measurements

Abstract

Depletion region modulation (DRM) effect is often observed in photoconductance lifetime measurements of crystalline silicon wafers passivated by dielectric films. This effect is closely related to the space-charge region electrostatically induced by fixed charges within the dielectric. This study proposes a model for dielectric-passivated c-Si wafers, which includes the DRM effect, to simulate and fit the effective lifetime vs excess minority carrier density curves obtained by quasisteady-state photoconductance techniques. The validity of the model is checked by applying it to different experimental samples, taking particular care of the mobility values of the surface carriers. It is, thus, demonstrated that the fixed charge within the dielectric film can be determined with improved accuracy and increased reliability if the DRM effect is included into the model.