Effect of different cap layers on the structure and optical properties of InAs/GaAs self-assembled quantum dot

Self-assembled InAs/GaAs quantum dot structures with different cap layers are grown by metal-organic chemical vapor deposition.The structure and optical properties of quantum dots are investigated using atomic force microscopy and photoluminescence.The cap layers sandwiched between quantum dots are composed of a low-temperature layer and a high-temperature layer.The comparative studies on low-temperature cap layer show that In graded InGaAs layer structure improves the uniformity of quantum dots,decreases coalescent islands and enhances photoluminescence intensity.Emission wavelength shifts from 1256.0 nm to 1314.4 nm when the thickness of graded InGaAs low-temperature cap layer increases form 6.8 nm to 12 nm.The research on high-temperature cap layer structure indicates that In graded InGaAs layer can increase photoluminescence intensity.