The impact of a double-cap procedure using two growth temperatures on the optical characteristics of InAs/InGaAsP/InP quantum dots (QDs) grown by metal-organic chemical vapor deposition has been investigated. With a combination of optimized thickness of the first cap layer and elevated growth temperature for the second cap layer, it is found that the photoluminescence (PL) linewidth of QDs can be significantly reduced from 124 meV to 87 meV at room temperature (RT). This reduction in PL linewidth is likely to be due to the enhanced As/P exchange reaction and indium migration at high growth temperature, which lead to a more uniform QD height distribution. Moreover, the uniformity of the PL peak intensity and peak energy on the wafer surface is evidently improved due to the higher material quality achieved when an elevated temperature is used for the SCL growth. (C) 2013 Elsevier B.V. All rights reserved.