The effects of the arrangement between InAs quantum dots and InGaAs strain-reducing layer (SRL) on the optical properties of quantum dot light emitting diodes are investigated. Electroluminescence wavelength longer than 1.3 mum is obtained as InAs quantum dots (QDs) ale covered with a thin InGaAs SRL. For the same sample, the full-width at half-maximum of the ground state emission peak is as narrow as 19 mcV at low injection current, and less than 40-meV even at saturation condition. It is also found that the slope efficiency of the diode is higher than that of the other samples in the linear region and its light output saturation level is higher because of the higher density of QDs.