Geometric current component in charge-pumping measurements

A detailed experimental and modeling study of the geometric current component in charge pumping measurements is carried out for bulk MOSFETs. Nand p-channel devices with various gate lengths and widths are studied. Electron and hole components in the charge-pumping current are separated by applying five terminal measurements. A transient two-dimensional numerical model is used for a rigorous analysis of the effect. A one-dimensional semi-analytical model of the free-carrier removal from the channel is developed and applied with proper boundary conditions at the channel ends. The usually applied results from the CCD-theory are found to be inadequate to model the geometric component in MOSFETs. The proposed semi-analytical model enables understanding of all effects observed in experiments and numerical modeling, and provides results which quantitatively agree with numerically calculated curves. The impact of the inversion gate bias, the pulse fail (rise) time and the junction reverse bias on the geometric component is explained. Both experiments and modeling show that the turn-off slew rate is the only parameter of the gate pulse practically relevant for the magnitude of the geometric component.