Optimizing the double-cap procedure for InAs/InGaAsP/InP quantum dots by metal-organic chemical vapor deposition

We report the optimization of the double-cap (DC) procedure for InAs/InGaAsP/InP quantum dots (QD) grown by metal-organic chemical vapor deposition. By using a combination of optimized thickness of the first cap layer and elevated growth temperature for the second cap layer, the photoluminescence (PL) linewidth of samples with five QD layers is significantly reduced from 124 meV to 87 meV at room temperature. Furthermore, the uniformity of the PL peak intensity and peak energy on the wafer surface is evidently improved. This distribution improvement is especially beneficial for improving device yield per wafer in device fabrication.