Publications (41)
Geometry effects at conductance quantization in quantum wires
G. KieÃlich, A. Wacker, E. Schöll
The transmission through quantum wires is studied within a noninteracting model taking into account the geometry of cleaved edge overgrowth devices. We show that the junction betwe…
Free carrier absorption in quantum cascade structures
F. Carosella, C. Ndebeka-Bandou, R. Ferreira +5
We show that the free carrier absorption in Quantum Cascade Lasers is very small and radically different from the classical Drude result on account of the orthogonality between the…
Correlation-induced conductance suppression at level degeneracy in a quantum dot
H. A. Nilsson, O. Karlström, M. Larsson +6
The large, level-dependent g-factors in an InSb nanowire quantum dot allow for the occurrence of a variety of level crossings in the dot. While we observe the standard conductance…
Probing confined phonon modes by transport through a nanowire double quantum dot
C. Weber, A. Fuhrer, C. Fasth +3
Strong radial confinement in semiconductor nanowires leads to modified electronic and phononic energy spectra. We analyze the current response to the interplay between quantum conf…
Shot noise of coupled semiconductor quantum dots
G. Kiesslich, A. Wacker, E. Schoell
The low-frequency shot noise properties of two electrostatically coupled semiconductor quantum dot states which are connected to emitter/collector contacts are studied. A master eq…
Transport in semiconductor superlattices: from quantum kinetics to terahertz-photon detectors
A. P. Jauho, A. Wacker, A. A. Ignatov
Semiconductor superlattices are interesting for two distinct reasons: the possibility to design their structure (band-width(s),doping, etc.) gives access to a large parameter space…
Simulation of Transport and Gain in Quantum Cascade Lasers
A. Wacker, S. -C. Lee, M. F. Pereira
Quantum cascade lasers can be modeled within a hierarchy of different approaches: Standard rate equations for the electron densities in the levels, semiclassical Boltzmann equation…
Controlling many-body effects in the midinfrared gain and THz absorption of quantum cascade laser structures
M. F. Pereira, S. -C. Lee, A. Wacker
A many-body theory based on nonequilibrium Green functions, in which transport and optics are treated on a microscopic quantum mechanical basis, is used to compute gain and absorpt…
Wavefronts may move upstream in doped semiconductor superlattices
A. Carpio, L. L. Bonilla, A. Wacker +1
In weakly coupled, current biased, doped semiconductor superlattices, domain walls may move upstream against the flow of electrons. For appropriate doping values, a domain wall sep…
Thermopower signatures and spectroscopy of the canyon of conductance suppression
G. Kiršanskas, S. Hammarberg, O. Karlström +1
Interference effects in quantum dots between different transport channels can lead to a strong suppression of conductance, which cuts like a canyon through the common conductance p…
Canyon of Current Suppression in an interacting two-level Quantum Dot
O. Karlström, J. N. Pedersen, P. Samuelsson +1
Motivated by the recent discovery of a canyon of conductance suppression in a two-level equal spin quantum dot system [Phys. Rev. Lett. , 186804 (2010)] the transport thr…
Signatures of Wigner Localization in Epitaxially Grown Nanowires
L. H. Kristinsdóttir, J. C. Cremon, H. A. Nilsson +5
It was predicted by Wigner in 1934 that the electron gas will undergo a transition to a crystallized state when its density is very low. Whereas significant progress has been made…
Current-voltage characteristic, stability, and self-sustained current oscillations in resonant-tunneling n-doped semiconductor superlattices
L. L. Bonilla, M. Kindelan, M. Moscoso +1
We review the statics and dynamics of electric-field domains on doped superlattices within a discrete drift model. A complete analysis of the construction and stability of stationa…
Coulomb scattering with remote continuum states in quantum dot devices
R. Wetzler, A. Wacker, E. Sch"oll
Electron capture and emission by Coulomb scattering in self-assembled quantum dot (QD) devices is studied theoretically. While the dependence of the Coulomb scattering (Auger) rate…
Quantum transport calculations for quantum cascade laser structures
S. C. Lee, A. Wacker
We apply a quantum transport theory based on nonequilibrium Green's functions to quantum cascade laser (QCL) structures, treating simultaneously the transmission through the inject…
Nonequilibrium Green's function theory for transport and gain properties of quantum cascade structures
S. -C. Lee, A. Wacker
The transport and gain properties of quantum cascade (QC) structures are investigated using a nonequilibrium Green's function (NGF) theory which includes quantum effects beyond a B…
Shot Noise in Tunneling through a Quantum Dot Array
G. Kiesslich, A. Wacker, E. Schoell +3
The shot noise suppression in a sample containing a layer of self-assembled InAs quantum dots has been investigated experimentally and theoretically. The observation of a non-monot…
A diagrammatic description of the equations of motion, current, and noise within the second-order von Neumann approach
O. Karlström, C. Emary, P. Zedler +5
We investigate the second-order von Neumann approach from a diagrammatic point-of-view and demonstrate its equivalence with the resonant tunneling approximation. Investigation of h…
Density-matrix theory of the optical dynamics and transport in quantum cascade structures: The role of coherence
C. Weber, A. Wacker, A. Knorr
The impact of coherence on the nonlinear optical response and stationary transport is studied in quantum cascade laser structures. Nonequilibrium effects such as pump-probe signals…
Inelastic quantum transport in superlattices: success and failure of the Boltzmann equation
A. Wacker, A. -P. Jauho, S. Rott +3
Electrical transport in semiconductor superlattices is studied within a fully self-consistent quantum transport model based on nonequilibrium Green functions, including phonon and…
A phonon scattering assisted injection and extraction based terahertz quantum cascade laser
E. Dupont, S. Fathololoumi, Z. R. Wasilewski +6
A novel lasing scheme for terahertz quantum cascade lasers, based on consecutive phonon-photon-phonon emissions per module, is proposed and experimentally demonstrated. The charge…
Dynamical bistability in quantum dot structures: The role of Auger processes
A. Rack, R. Wetzler, A. Wacker +1
Bistability in quantum dot structures is examined by a drift-diffusion model in combination with electron capture and emission processes. Our simulations provide a dynamic scenario…
Quantum-mechanical wavepacket transport in quantum cascade laser structures
S. -C. Lee, F. Banit, M. Woerner +1
We present a viewpoint of the transport process in quantum cascade laser structures in which spatial transport of charge through the structure is a property of coherent quantum-mec…
Quantifying the impact of phonon scattering on electrical and thermal transport in quantum dots
B. Goldozian, G. Kiršanskas, F. A. Damtie +1
We report the inclusion of phonon scattering to our recently established numerical package QmeQ for transport in quantum dot systems. This enables straightforward calculations for…
Analyzing capacitance-voltage measurements of vertical wrapped-gated nanowires
O. Karlström, A. Wacker, K. Nilsson +4
The capacitance of arrays of vertical wrapped-gate InAs nanowires are analyzed. With the help of a Poisson-Schr"odinger solver, information about the doping density can be obtained…
Current-voltage characteristic and stability in resonant-tunneling n-doped semiconductor superlattices
A. Wacker, M. Moscoso, M. Kindelan +1
We review the occurrence of electric-field domains in doped superlattices within a discrete drift model. A complete analysis of the construction and stability of stationary field p…
Hot Carrier Nanowire Transistors at the Ballistic Limit
M. Kumar, A. Nowzari, A. R. Persson +7
We demonstrate experimentally non-equilibrium transport in unipolar quasi-1D hot electron devices reaching ballistic limit. The devices are realized with heterostructure engineerin…
Gain and Loss in Quantum Cascade Lasers
A. Wacker, S. -C. Lee
We report gain calculations for a quantum cascade laser using a fully self-consistent quantum mechanical approach based on the theory of nonequilibrium Green functions. Both the ab…
Two-well quantum cascade laser optimization by non-equilibrium Green's function modelling
M. Franckié, L. Bosco, M. Beck +5
We present a two-quantum well THz intersubband laser operating up to 192 K. The structure has been optimized with a non-equilibrium Green's function model. The result of this optim…
Self-Consistent Theory of the Gain Linewidth for Quantum Cascade Lasers
F. Banit, S. -C. Lee, A. Knorr +1
The linewidth in intersubband transitions can be significantly reduced below the sum of the lifetime broadening for the involved states, if the scattering environment is similar fo…
Positive Correlations in Tunneling through coupled Quantum Dots
H. Sprekeler, G. Kiesslich, A. Wacker +1
Due to the Fermi-Dirac statistics of electrons the temporal correlations of tunneling events in a double barrier setup are typically negative. Here, we investigate the shot noise b…
Electrically tunable GHz oscillations in doped GaAs-AlAs superlattices
J. Kastrup, R. Hey, K. H. Ploog +5
Tunable oscillatory modes of electric-field domains in doped semiconductor superlattices are reported. The experimental investigations demonstrate the realization of tunable, GHz f…
Chaotic front dynamics in semiconductor superlattices
A. Amann, J. Schlesner, A. Wacker +1
We analyze the dynamical evolution of the current and the charge density in a superlattice for fixed external dc voltage in the regime of self-sustained current oscillations, using…
Chaotic Behavior of Quantum Cascade Lasers at Ignition
D. E. Ãnder, A. A. S. Kalaee, D. O. Winge +1
The ignition of Quantum Cascade Lasers can occur from a state of oscillating fie ld domains. Here, the interplay between lasing and the kinetics of traveling dom ain boundaries pro…
Self-consistent Coulomb effects and charge distribution of quantum dot arrays
R. Wetzler, A. Wacker, E. Schöll
This paper considers the self-consistent Coulomb interaction within arrays of self-assembled InAs quantum dots (QDs) which are embedded in a pn structure. Strong emphasis is being…
A hybrid model for chaotic front dynamics: From semiconductors to water tanks
A. Amann, K. Peters, U. Parlitz +2
We present a general method for studying front propagation in nonlinear systems with a global constraint in the language of hybrid tank models. The method is illustrated in the cas…
Coulomb effects in tunneling through a quantum dot stack
H. Sprekeler, G. Kiesslich, A. Wacker +1
Tunneling through two vertically coupled quantum dots is studied by means of a Pauli master equation model. The observation of double peaks in the current-voltage characteristic in…
Counting statistics and decoherence in coupled quantum dots
G. Kiesslich, P. Samuelsson, A. Wacker +1
We theoretically consider charge transport through two quantum dots coupled in series. The corresponding full counting statistics for noninteracting electrons is investigated in th…
High-Frequency Impedance of Driven Superlattices
A. -K. Jappsen, A. Amann, A. Wacker +2
The complex impedance of a semiconductor superlattice biased into the regime of negative differential conductivity and driven by an additional GHz ac voltage is computed. From a si…
Fingerprints of spatial charge transfer in Quantum Cascade Lasers
R. Nelander, A. Wacker, M. F. Pereira +7
We show that mid infrared transmission spectroscopy of a quantum cascade laser provides clear cut information on changes in charge location at different bias. Theoretical simulatio…
Theoretical analysis of spectral gain in a THz quantum cascade laser: prospects for gain at 1 THz
S. -C. Lee, A. Wacker
In a recent Letter [Appl. Phys. Lett. 82, 1015 (2003)], Williams et al. reported the development of a terahertz quantum cascade laser operating at 3.4 THz or 14.2 meV. We have calc…