Epitaxial growth of III–V materials on silicon (Si) substrates is one of the most promising techniques for generating coherent light on Si and offers a low-cost and high-yield solution for Si photonics. The main challenge of this technique is the large material dissimilarity between group IV and III–V compounds. These differences between group IV and III–V tend to produce various types of defects which all generate non-radiative recombination centres and dramatically undermine the promise of III–V materials. Multiple strategies for novel epitaxial growth technologies have been employed in order to reduce the defect density, resulting in high-quality III–V materials on Si. Very recently, III–V quantum-dot (QD) structures have drawn increasing attention for the implementation of compound semiconductor lasers on Si, due to their low threshold current density and reduced temperature sensitivity. In addition, QD structures have also been proven to be less sensitive to defects than conventional bulk materials and quantum well structures, mainly due to the stronger carrier localisation and hence reduced interaction with the defects. As a result, high-performance Si-based QD laser devices have been developed intensively. In order to fully utilize the advantages of Si photonics, the next challenge is to monolithically integrate the high-performance III-V QD lasers with other components, such as modulators and waveguides on a Si platform for information processing and transmission systems.