Characterization of InGaAs QDs grown on GaAs and Si substrate

III-V semiconductor quantum dots (QDs) have shown significant advantages, such as low threshold current, outstanding thermal stability and reduced sensitivity to defects, for application of optoelectronic devices due to their δ-like discrete density of states. Furthermore, integrating such high-quality QDs light emitting source onto a commercial silicon platform could potentially enable the realisation of optical inter-chip connection. Among the methods developed for integration of III-V on silicon, direct epitaxy grown III-V on silicon is extremely challenging due to the large lattice mismatch, thermal expansion coefficient mismatch and the difference between polar and non-polar materials. Typically, lattice mis-matched materials relieve strain by forming misfit defects leading to the formation of threading dislocations, which can propagate into over-lying active layers of devices and damage device performance.
In this thesis, characterization the InGaAs QDs epitaxy grown on GaAs substrate and Si substrate structure has been performed to enable a deeper understanding of the performance of a c.w. operated InGaAs QD laser grown on a Si substrate.
Rapid thermal annealing, including post growth annealing and in-situ thermal cycle annealing has been utilized to reduce defect nucleation and propagation. The positive effect of post growth annealing on InGaAs QDs monolithically grown on Si substrate structure was investigated. The annealing effect on the In-Ga inter-diffusion and the change in the size of QDs has been studied as a function of temperature by HAADF-STEM image and EDX analysis, combined with PL optical spectroscopy. Furthermore, the annealing effect on GaAs/Si and AlAs/Si interface, and threading dislocation density has also been demonstrated. The densities of threading dislocations have been measured as a function of annealing temperature.
The in-situ thermal cycle annealing and optimize of nucleation layer have successfully reduced the threading dislocation density cumulating in the fabrication of a c.w. lasing InGaAs QD laser grown on a Si substrate representing an important step for Si photonics integration.