Ab initiooptoelectronic properties of SiGe nanowires: Role of many-body effects

Abstract

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

Role of vacancies to p-type semiconducting properties of SiGe nanowires

“…[26][27][28] Amato et al studied structure stabilities, electronic properties, and quantum connement effects of the different types of SiGe NW based on rst-principle calculations. [29][30][31][32][33] They predicted that the Ge core Si shell NW are very stable energetically, and that efficient electron and hole doping can be easily realized because of the band offset in the type-II heterojunction of the Ge core Si shell NW. 34,35 Following Amato's work, we have systematically studied substitution doping in various compositionally abrupt Si/Ge NW using the rst-principle method because of the presence of type-II band offsets in other types of compositionally abrupt Si/Ge NW in addition to the Ge core Si shell NW.…”

Band structure analysis in SiGe nanowires

“…The role that SiGe NSs can play in various technological fields has been clearly demonstrated, for example regarding the possibility to use these nanostructures to realize electronic [18,19], photovoltaic [20], optoelectronic [21] and thermoelectric [22] devices. During the last decade an increasing attention, both from the experimental [18,[23][24][25][26][27][28][29][30][31] and theoretical point of view [14,15,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46], has been dedicated to SiGe nanowires (SiGe NWs), that are one-dimensional nanoalloys that can be synthesized using top-down [24,25] or bottom-up [5,26,27] approaches and for which it is possible to reach a precise control of the size, the morphology and the electronic properties. Several types of SiGe NWs have been grown: core-shell NWs [5], which are radial heterostructures, synthesized firstly by the Lieber's group in 2002; axial heterojunctions [31], that present a sharp interface between Si and Ge along the axial direction of the wire; random NWs [16], where the relative configuration of Si and Ge atoms is completely random; triangular shaped NWs …”

“…Several types of SiGe NWs have been grown: core-shell NWs [5], which are radial heterostructures, synthesized firstly by the Lieber's group in 2002; axial heterojunctions [31], that present a sharp interface between Si and Ge along the axial direction of the wire; random NWs [16], where the relative configuration of Si and Ge atoms is completely random; triangular shaped NWs [23], produced in different ways and, very recently, object of theoretical investigation [46]. In our previous works we have analyzed an innovative geometry for the SiGe NWs [14,15,42,44], characterized by the presence of a sharp interface in the transverse cross-section of the wire (in the following, we will call this geometry abrupt NWs). We have demonstrated how this type of geometry (in particular through the presence of a sharp interface) can originate very interesting electronic and optical properties.…”

Optical absorption modulation by selective codoping of SiGe core-shell nanowires

“…[30][31][32][33] We are then convinced that the present work can provide a first, qualitatively correct, description of the optical properties of these SiGe codoped nanowires. Furthermore, in a previous work, 34 we explicitly calculated the GW corrections for pure SiGe core-shell NWs showing that they can be obtained as a weighted average, on the relative atomic composition, of the corrections of pure Si and Ge nanowire of the same diameter. Though we cannot state that this rule is valid also in the case of the codoped wire, we refer the reader to that work 34 to have an idea of the numerical error of the LDA results with respect to the real electronic gaps of these one-dimensional nanostructures.…”