Vertical strain-induced dot size uniformity and thermal stability of InAs/GaAsN/GaAs coupled quantum dots

We report, for the first time, 10-layer InAs/GaAsN/GaAs quantum dots (QDs) by varying the GaAs layer thickness and investigate their optical properties. Due to propagation of strain field from bottom to top, multiple stacking of self-assembled QDs helps special ordering of QDs on surface resulting in dot size uniformity. InAs coupled QDs with GaAsN/GaAs spacers of 2/10 nm exhibited a bimodal distribution with narrow linewidths and low As-related deep level defect peak intensity, attributable to good optical quality of QDs. N-like local vibrational mode in Raman spectroscopy was found to be consisted of ten oscillation fringes, possibly because of ten periods of GaAsN layer used in QD-heterostructures. Higher strain coupling resulted in lesser blue-shift with increasing annealing temperature as compared to the lower coupling, leading to thermal stability of coupled QDs. Coupled QDs exhibiting narrow linewidths and thermal stability could be employed in fabrication of photodetectors.