The doping characteristics and carrier transport in a GaAs p-n junction were visualized with a approximately 10 nm spatial resolution, using light-modulated scanning tunneling spectroscopy. The dynamics of minority carriers under operating conditions, such as recombination, diffusion, and electric field induced drift, which had previously been analyzed on the basis of empirical electric properties, were successfully examined on the nanoscale. These results provide a solid basis for elucidating the mechanism of the carrier transport properties predicted by using the macroscopic analysis.