331 research outputs found
Electron beam induced current in InSb-InAs nanowire type-III heterostructures
InSb-InAs nanowire heterostructure diodes investigated by electron beam induced current (EBIC) demonstrate an unusual spatial profile where the sign of the EBIC signal changes in the vicinity of the heterointerface. A qualitative explanation confirmed by theoretical calculations is based on the specific band diagram of the structure representing a type-III heterojunction with an accumulation layer in InAs. The sign of the EBIC signal depends on the specific parameters of this layer. In the course of measurements, the diffusion length of holes in InAs and its temperature dependence are also determined
Electrical properties and band diagram of InSb-InAs nanowire type-III heterojunctions
The electrical properties of nanowire-based n-InSb-n-InAs heterojunctions were investigated theoretically and experimentally. Analysis of the current-voltage characteristics showed that the current through the heterojunction is caused mostly by generation-recombination processes in the InSb and at the heterointerface. Due to the partially overlapping valence band of InSb and the conduction band of InAs, the second process is fast and activationless. Theoretical analysis showed that, depending on the heterojunction parameters, the flux of non-equilibrium minority carriers may have a different direction, explaining the experimentally observed non-monotonic coordinate dependence of the electron beam induced current
Bifurcations and chaos in semiconductor superlattices with a tilted magnetic field
We study the effects of dissipation on electron transport in a semiconductor
superlattice with an applied bias voltage and a magnetic field that is tilted
relative to the superlattice axis.In previous work, we showed that although the
applied fields are stationary,they act like a THz plane wave, which strongly
couples the Bloch and cyclotron motion of electrons within the lowest miniband.
As a consequence,the electrons exhibit a unique type of Hamiltonian chaos,
which creates an intricate mesh of conduction channels (a stochastic web) in
phase space, leading to a large resonant increase in the current flow at
critical values of the applied voltage. This phase-space patterning provides a
sensitive mechanism for controlling electrical resistance. In this paper, we
investigate the effects of dissipation on the electron dynamics by modifying
the semiclassical equations of motion to include a linear damping term. We
demonstrate that even in the presence of dissipation,deterministic chaos plays
an important role in the electron transport process. We identify mechanisms for
the onset of chaos and explore the associated sequence of bifurcations in the
electron trajectories. When the Bloch and cyclotron frequencies are
commensurate, complex multistability phenomena occur in the system. In
particular, for fixed values of the control parameters several distinct stable
regimes can coexist, each corresponding to different initial conditions. We
show that this multistability has clear, experimentally-observable, signatures
in the electron transport characteristics.Comment: 14 pages 11 figure
Effect of temperature on resonant electron transport through stochastic conduction channels in superlattices
We show that resonant electron transport in semiconductor superlattices with
an applied electric and tilted magnetic field can, surprisingly, become more
pronounced as the lattice and conduction electron temperature increases from
4.2 K to room temperature and beyond. It has previously been demonstrated that
at certain critical field parameters, the semiclassical trajectories of
electrons in the lowest miniband of the superlattice change abruptly from fully
localised to completely unbounded. The unbounded electron orbits propagate
through intricate web patterns, known as stochastic webs, in phase space, which
act as conduction channels for the electrons and produce a series of resonant
peaks in the electron drift velocity versus electric field curves. Here, we
show that increasing the lattice temperature strengthens these resonant peaks
due to a subtle interplay between thermal population of the conduction channels
and transport along them. This enhances both the electron drift velocity and
the influence of the stochastic webs on the current-voltage characteristics,
which we calculate by making self-consistent solutions of the coupled electron
transport and Poisson equations throughout the superlattice. These solutions
reveal that increasing the temperature also transforms the collective electron
dynamics by changing both the threshold voltage required for the onset of
self-sustained current oscillations, produced by propagating charge domains,
and the oscillation frequency.Comment: 8 figures, 12 page
Modeling of dielectric hysteresis loops in ferroelectric semiconductors with charged defects
We have proposed the phenomenological description of dielectric hysteresis
loops in ferroelectric semiconductors with charged defects and prevailing
extrinsic conductivity. Exactly we have modified Landau-Ginsburg approach and
shown that the macroscopic state of the aforementioned inhomogeneous system can
be described by three coupled equations for three order parameters. Both the
experimentally observed coercive field values well below the thermodynamic one
and the various hysteresis loop deformations (constricted and double loops)
have been obtained in the framework of our model. The obtained results
quantitatively explain the ferroelectric switching in such ferroelectric
materials as thick PZT films.Comment: 21 pages, 10 figures, sent to Journal of Physics: Condensed Matte
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High-field terahertz response of graphene
We investigate the response of multi-layer epitaxial graphene and chemical vapor deposition (CVD)-grown single-layer graphene to strong terahertz (THz) fields. Contrary to theoretical predictions of strong nonlinear response, the transmitted fields exhibit no harmonic generation, indicating that the nonlinear response is limited by fast electron thermalization due to carrier-carrier scattering. The fast electron heating gives rise to large THz transmission enhancement (>15%) in single-layer CVD graphene at high THz fields (E-THz > 10 kV cm⁻¹). The nonlinear effects exhibit non-Drude behavior in the THz conductivity, where THz fields induce extreme non-equilibrium electron distributions.Keywords: Spectroscopy, Generation, Gas, Transistor
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