An investigation into the structural, electronic and optical properties of Si, Ge, and Si 1-x Ge x for different compositions was conducted using first-principles calculations based on density functional theory (DFT). The total energies were calculated within the full-potential linear muffin-tin orbital (FP-LMTO) method augmented by a plane-wave basis (PLW), implemented in Lmtar code. The effects of the approximations to the exchange-correlation energy were treated by the local density approximation (LDA). From our simulation results, it is found that the theoretical ground-state parameters, the band structure, the density of states (DOS), the chemical bonding and the optical properties agree well with the experiment and other theoretical calculations. The accuracies found from the present calculations allow us to describe the properties of the electronic as well as the optoelectronic devices based on the Si 1-x Ge x alloy.

This paper reviews the basic properties of the SiGe alloy, presents some new results on its electronic and optical properties, and discusses the approach that has been followed to model quantum wells containing SiGe layers for applications in quantum cascade lasers. The shape of the confining potential, the subband energies and their eigen envelope wave functions are calculated by solving a one-dimensional Schrödinger equation. The calculations of optical parameters are used to optimize the Si/SiGe quantum cascade structures. Our results are found to be in good agreement with other calculations.