By means of partially ionized MBE (PI-MBE), n+/p silicon solar cells have been fabricated. The surface layer epitaxially grown on a p-type bulk silicon substrate (ps0.540.0 ohm-cm) could be heavily doped (p1.01.0-3 ohm-cm; 5.01019 cm-3 carrier concentration) using As with the substrate temperature higher than or equal to 700. The cells were evaluated with IV characteristics under AM1 illumination and spectral responses obtained by a computer aided proofreading method. It has been found that the cell conversion efficiency η and the fill factor F. F. are 11.012.0% and 0.700.75, respectively.