Quantitative evaluation of the dopant concentration across silicon p–n junctions has been performed on oxide-passivated surfaces by using tunneling current mapping in the constant-gap mode of a multimode scanning probe microscope (MSPM). A distinct difference between regions with different impurity concentrations was observed in tunneling current maps when a constant tunneling gap was maintained by using repulsive force acting on the MSPM probe. To extract impurity profiles, the results of three-dimensional device simulations within the current continuity model were compared with measured bias-dependent current profiles. The obtained impurity profiles showed agreement with the actual donor concentration in the p–n junction region. The results demonstrate the applicability of the method for quantitative analysis of the local impurity distribution in modern semiconductor devices with improved sensitivity and nanometer spatial resolution. # 2013 The Japan Society of Applied Physics