Porous silicon (PS) is doped with erbium by electrochemical anodisation. The penetration of erbium into the PS layer is confirmed by Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray (EDX) measurements. Efficient green and infrared emissions were observed at room temperature. The investigations are focused on the evolutions versus temperature and pump intensity of the green photoluminescence (PL) corresponding to the S-4(3/2) -> I-4(15/2) transition. It was found that an erbium related level defect can be involved on the excitation and emission processes of erbium. Pump intensity dependent PL studies revealed that for the electrochemical incorporation, most of the Er 3, ions are localized inside the Si nanocrystallites and not in stoichiometric SiO2. The optical cross-section is close to that of erbium in Si nanocrystallites. (c) 2005 Elsevier B.V. All rights reserved.