The preparation of well-defined cross-sectional samples is critical for the quantitative analysis of p-n junctions in semiconductor devices by electron holography. A wedge is a good shape for the geometry of the cross section that is suitable for mapping and characterizing one-dimensional p-n junctions, especially those with lower doping levels. The method we used to prepare such cross sections involved focused-ion-beam milling and we describe it in detail. Following this, we could easily fabricate well-defined wedge-shaped cross sections with different given angles within a very short time. The use of such cross sections allowed us to clearly map implanted Si/Si p-n junction structures with lower dopant concentrations with off-axis electron holography. (C) 2003 American Vacuum Society.