Ab initio optoelectronic properties of SiGe nanowires: Role of many-body effects

The self-energy and electron-hole interaction corrections to the one-particle approximation for SiGe nanowireshave been calculated for different geometries and diameters. We show that, at fixed nanowire diameterand orientation, the self-energy corrections for the SiGe nanowires can be obtained as a weighted average, onthe relative composition of one type of atom with respect to the total numbers of atoms in the unit cell, of thecorrections for the pure Si and Ge nanowires, thus circumventing cumbersome computations and allowing adirect and practical determination of the electronic band gap. Moreover we show that particular geometricalconfigurations are at the origin of an enhancement of the optical oscillator strength that should be important foroptoelectronic applications.