14 research outputs found
Interface states in junctions of two semiconductors with intersecting dispersion curves
A novel type of shallow interface state in junctions of two semiconductors
without band inversion is identified within the envelope function
approximation, using the two-band model. It occurs in abrupt junctions when the
interband velocity matrix elements of the two semiconductors differ and the
bulk dispersion curves intersect. The in-plane dispersion of the interface
state is found to be confined to a finite range of momenta centered around the
point of intersection. These states turn out to exist also in graded junctions,
with essentially the same properties as in the abrupt case.Comment: 1 figur
Quantum Well Based on Graphene and Narrow-Gap Semiconductors
We consider the energy spectrum of the planar quantum well which consisted of
two ribbons of narrow-gap semiconductors and a graphene ribbon between ones. It
is shown that the gapless mode appears only in case of inverted narrow-gap
semiconductors. Spin splitting of the energy spectrum for a nonsymmetric
quantum well is calculated taking into account a specificity of graphene. We
investigate interface states and optical transitions. It is shown that the
optical transitions are possible only with a conservation of a parity.Comment: 13 pages, 2 figures, 1 tabl
Size Quantization in Planar Graphene-Based Heterostructures: Pseudospin Splitting, Interface States, and Excitons
A planar quantum-well device made of a gapless graphene nanoribbon with edges
in contact with gapped graphene sheets is examined. The size-quantization
spectrum of charge carriers in an asymmetric quantum well is shown to exhibit a
pseudospin splitting. Interface states of a new type arise from the crossing of
dispersion curves of gapless and gapped graphene materials. The exciton
spectrum is calculated for a planar graphene quantum well. The effect of an
external electric field on the exciton spectrum is analyzed.Comment: 15 pages, 14 figure