The optical activation of Si nanowires (SiNWs) by the coating of Er3+ doped binary silicon-aluminum oxides (Si-Al oxides) films derived from sol-gel solutions is reported. Continuous and crack-free Si-Al oxide film could be successfully coated onto an Si substrate where the SiNWs were grown. The strong Er3+ luminescence of 1.534 mu m from the SiNWs was observed at a high Er concentration (5 at.%). These results suggest that the Al-Si oxide film makes it possible to realize a strong Er3+ luminescence by excluding concentration quenching while at the same time improving the quality of film. (c) 2007 Elsevier B.V. All rights reserved.