Theoretical and experimental study of charge carrier kinetics in crystalline silicon

Abstract

A model simulating excess charge carrier kinetics in Si wafers was developed taking into account space charge fields and surface recombination. This model was applied to experimental data obtained by contactless transient and frequency resolved photoconductivity measurements of silicon wafers with accumulation or depletion layers at the surface. It is shown that a surface accumulation layer has only a minor influence and surface recombination can be analyzed with a surface recombination velocity weakly depending on the excess carrier concentration. At low injection level a surface depletion layer leads to a strongly nonlinear behavior of the photoconductivity due to excess charge carriers stored in the space charge region. The presence of these charge carriers is also revealed by the tail of the transient photoconductivity signal characterized by a decay time longer than the volume lifetime. At higher injection level the contribution of these charge carriers to the photoconductivity can be neglected and the data can be analyzed with the (differential) surface recombination velocity.