The electronic structure and optical properties of Ge-core/Si-shell nanocrystal or quantum dot (QD) are investigated
using the atomistic tight binding method as implemented in NEMO3D. The thermionic lifetime that
governs the hole leakage mechanism in the Ge/Si QD based laser, as a function of the Ge core size and strain, is
also calculated by capturing the bound and extended eigenstates, well below the band edges. We also analyzed
the eect of core size and strain on optical properties such as transition energies and transition rates between
electron and hole states. Finally, a quantitative and qualitative analysis of the leakage current due to the hole
leakage through the Ge-core/Si-shell QD laser, at dierent temperatures and Ge core sizes, is presented.