We have derived an analytical effective-mass model and employed first-principles density functional theory to study the spatial confinement of carriers in core-shell and multishell structured semiconductor nanowires. The band offset effect is analyzed based on the subband charge density distributions, which is strongly dependent upon the strain relaxation. First-principles calculation results for spatially confined Si/Ge and GaN/GaP nanowires indicate accumulation of a Ge-core hole gas and a GaN-core electron gas, respectively, in agreement with experimental observations.
The electronic structure characteristics of supramolecular functionalization of graphene nanoribbons with π-conjugated polymers are investigated using first-principles density functional theory. Noncovalent polymer functionalization leads to distinct changes in the electronic properties, particularly the band gaps of metallic and semimetallic graphene nanoribbons. A detailed analysis of band alignments reveals a profound level hybridization for ribbons with various shaped edges and spin density waves near the edges of zigzag ribbons. The extracted planar polymer conformations and the disappearance of the metallic behavior are in conformity with experimental observations.
Complementary doped donor and acceptor dipoles effectively generate confinement potentials for carriers across a p-type/intrinsic/n-type coaxial nanowire due to the lineup of charge neutrality level. In order to verify this physical picture, we employ first-principles density functional theory to study the confinement of electrons and holes in complementary boron (p-type) and phosphorus (n-type) doped coaxial silicon nanowires. An analysis of the charge density distributions reveals that the electrons and holes are spatially separated in core and outer shell regions, respectively, in conformity with a type-II lineup of band structures.
The electronic structure characteristics of silicon nanowires under tensile and compressive strain are studied using first-principles density functional theory. The unique wirelike structure leads to distinct hole distributions in the core and shell regions, which can be characterized by the electronic band structures of the light-hole and heavy-hole states. The onset transition pressure for silicon nanowires is shown to be lower than the value of bulk counterpart, in conformity with experimental observations. These results demonstrate that the impact of strain on the electronic characteristics is important for nanodevice applications.
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