Space-charge region-dominated steady-state photoconductance in low-lifetime Si wafers

We investigate the steady-state photoconductance of an oxidized low-lifetime monocrystalline Si wafer with an inversion layer at its surfaces. Photogenerated electrons and holes reduce the band bending and decrease the width of the carrier depleted space-charge region. Mobile charge carriers are stored on both sides of the space-charge region and dominate the photoconductivity at a low illumination intensity. This charge storage effect disappears under accumulation. We present an analytic model for the experimental observations. It is necessary to account for the charge storage effect when deducing low (<10 μs) minority carrier lifetimes on surface-inverted solar Si wafers from one-sun steady-state photoconductance measurements.