| Nanostructures have become an important field of study in the past few years for their interesting physical characteristics due to features' size and quantum confinement, which have added new potential applications to the scope of electrical and optical devices. Quantum dots (QDs) in specific have the ability to confine electrons in three dimensions resulting in many advantages over other materials. However, many applications like detectors, low-threshold lasers, photonic crystals...etc. require a high uniformity in size, shape and distribution of QDs in order to prove their advantages. Due to the self-assembly process of forming QDs, inhomogeneous broadening in size and shape has degraded their device properties. Therefore, the need for controlling the size, shape and distribution of QDs has become an important area of research in the recent years.; Vertically stacking QDs layers at relatively high temperature and low indium composition allows them to align laterally in chains of uniform sized and shaped dots. This is because the dots in a certain layer would feel the ones underneath if the spacer layer between them is reduced to a certain extent. Also growing the stacked dots. This kind of ordering is anisotropic due the nature of GaAs (001) substrate. While isotropic ordering can be achieved by lithography techniques, our motivation is to achieve such ordering by controlling the growth parameters on GaAs without any processing. This is done by changing different growth conditions like substrate temperature, indium composition, background flux, and spacer layer thickness in a systematic way to optimize desired growth parameters. Multi-layer InGaAs QDs have been grown under As 2 flux and have shown a good hexagonal 2D ordering of dots that are separate from each other. They also have been characterized by a narrow photoluminescence emission as low as 23 meV. This experimental investigation not only has made it possible to achieve a nice 2D isotropic ordering of QDs on GaAs (001), which is a very challenging task facing QDs, but also has improved their optical properties. |
