A self-organized In0.5 Gao.sAs/GaAs quantum island structure emitting at 1.35μm at room temperature has beensuccessfully fabricated by molecular beam epitaxy via cycled (InAs)1/ ( GaAs)1 monolayer deposition method. Thephotoluminescence measurement shows that a very narrow linewidth of 19.2 meV at 300 K has been reached for the first time, indicating effective suppression of inhomogeneous broadening of optical emission from the Ino.5 Gao.sAsisland structure due to indium segregation reduction by introducing an AlAs layer and the strain reduction byinserting an Ino.2Gao.8As layer overgrown on the top of islands. The mound-like morphology of the islandselongated along the [110] azimuth are observed by the atomic force microscopy measurement, which revealsthe fact that strain in the islands is partially relaxed along the [110] direction. Our results present importantinformation for the fabrication of 1.3 μm wavelength quantum dot devices.