ABSTRACT
The high-quality germanium (Ge) films on silicon (Si) substrates have received much interest because of its compatibility with the well-established Si-based technology and their relevant applicability in electronics and opto-electronics devices. The growth of high-quality Ge films on the Si substrate is difficult due to the existence of the lattice mismatch between Ge and Si crystals, which gives rise to a rough surface morphology and a high density of defects. This chapter reviews the first-principles density-functional study that reveals atomic structures, stabilities and electronic structures of various Ge films deposited on Si (001) substrates. The energetics associated with the layer-by-layer growth of the Ge films on the Si substrate is examined, which is used for clarifying the strain-relaxation mechanism and the introduction of the 90° misfit dislocation. The scanning tunneling microscopy images of various Ge films are demonstrated and the possibility to observe the core structure of the 90° dislocation is exhibited.
