Disorder-free localization around the conduction band edge of crossing and kinked silicon nanowires

Abstract

We explore ballistic regime quantum transport characteristics of oxide-embedded crossing and kinked silicon nanowires (NWs) within a large-scale empirical pseudopotential electronic structure framework, coupled to the Kubo-Greenwood transport analysis. A real-space wave function study is undertaken and the outcomes are interpreted together with the findings of ballistic transport calculations. This reveals that ballistic transport edge lies tens to hundreds of millielectron volts above the lowest unoccupied molecular orbital, with a substantial number of localized states appearing in between, as well as above the former. We show that these localized states are not due to the oxide interface, but rather core silicon-derived. They manifest the wave nature of electrons brought to foreground by the reflections originating from NW junctions and bends. Hence, we show that the crossings and kinks of even ultraclean Si NWs possess a conduction band tail without a recourse to atomistic disorder.

Strongly scale-dependent charge transport from interconnections of silicon quantum dots and nanowires

“…This is so because when QDs are percolated, free charge carriers that are generated within a cluster are expected to be delocalized since they are now free to move over larger distances in a cluster of QDs. [11,[18][19][20] However, this does not mean that there is no possibility for charge carriers to recombine after the separation. On the contrary, there is another mechanism, active simultaneously, that increases the chances of recombination with other charge-carrier pairs generated elsewhere within the random network: the nanowires in this random network structure are far from being straight, in contrast to conventional nanowires; rather, they are heavily "undulated wires," as revealed by APT imaging [ Fig.…”

“…This suggests that these free charge carriers have to transport through a tortuous route, where the conduction and valence band edges vary spatially along the network. [19,20] This may introduce additional potential barriers to be overcome by the carriers, but at the same time when carriers flow through these narrower sections, they encounter not only higher resistance, but are also confined more tightly, which, in turn, increases the probability of radiative recombination. [19,20] These two seemingly contradictory mechanisms are at work simultaneously thanks to the random connections of the network, which allows simultaneous expression of quantum confinement and good electrical conduction features.…”

Electron ground state g factor in embedded InGaAs quantum dots: An atomistic study

“…In our case we employ the so-called linear combination of bulk bands (LCBB) which handles such atomic numbers with reasonable computational budget [56]. In the past, we used it in nanocrystals for the linear optical response [57], third-order nonlinear optics [58], electroabsorption [59], and coherent population transfer [60], and in nanowire structures for electronic structure [61] and ballistic transport [62].…”

Electron ground state $g$ factor in embedded InGaAs quantum dots: An atomistic study

“…In our case we employ the so-called linear combination of bulk bands (LCBB) which handles such atomic numbers with reasonable computational budget [51]. In the past, we used it in nanocrystals for the linear optical response [52], thirdorder nonlinear optics [53], electroabsorption [54], and coherent population transfer [55], and in nanowire structures for electronic structure [56] and ballistic transport [57]. To the best of our knowledge this is the first application of the LCBB method to the study of g-factor in semiconductors.…”