The Experts below are selected from a list of 39399 Experts worldwide ranked by ideXlab platform
P Vogl - One of the best experts on this subject based on the ideXlab platform.
-
real space multiband Envelope Function approach without spurious solutions
Physical Review B, 2011Co-Authors: T Eissfeller, P VoglAbstract:The Envelope-Function approach for mesoscopic electronic structure calculations is plagued by spurious solutions that originate in the ill representation of first-order derivatives in real-space bases. We present a symmetry-adapted finite element approach for multiband k · p Envelope-Function Hamiltonians that is manifestly free from spurious solutions, numerically efficient, and easy to implement. In addition, a gauge-invariant extension to this method is developed for problems involving magnetic fields. We predict the electrical exciton g-factor tuning in single InAs/GaAs embedded quantum dots to be significantly larger than previously found.
-
full band Envelope Function approach for type ii broken gap superlattices
Physical Review B, 2009Co-Authors: Till F M Andlauer, P VoglAbstract:We present a charge self-consistent mesoscopic electronic-structure method for type-II broken-gap superlattices that is based on the multiband k ·p Envelope-Function method. This scheme avoids the separate classification and occupation of electron and hole states that causes the standard effective-mass theory to fail once conduction- and valence-band states strongly intermix. The computational efficiency of Envelope-Function methods is maintained. Free or bound charge-carrier redistributions can be taken into account self-consistently. With this method that we term as full-band Envelope-Function approach, we calculate effective band gaps, effective masses, and optical transition energies of InAs/GaSb superlattices as a Function of the layer width. Good agreement with experiment is obtained. We also discuss semiconductor to semimetal transitions in wide layer structures. We find the charge carriers to form a two-dimensional gas of approximately massless Dirac particles at a critical layer width.
-
gauge invariant discretization in multiband Envelope Function theory and g factors in nanowire dots
Physical Review B, 2008Co-Authors: Till F M Andlauer, Richard Morschl, P VoglAbstract:We present a gauge-invariant discretization scheme for the multiband Envelope Function approximation including strain as well as relativistic effects. Our procedure is based on Wilson's formulation of gauge theories. The magnetic field couples to the Envelope Functions via phase factors that result from spatial discretization of the gauge covariant derivative. These phase factors contain a discretized curve integral over the vector potential. In addition, the carrier's spin couples to the magnetic field via a Zeeman term. In the case of infinitesimal grid spacings, our method becomes equivalent to the minimal substitution method. Applying our procedure, we calculate the effective electron and hole $g$ tensor of InAs/InP nanowire dots and obtain excellent agreement with experimental data. We show that the correct momentum operator ordering in the Hamiltonian grossly affects the hole $g$ factors. Furthermore, we investigate the influence of strain on $g$ factors and nonlinear Zeeman splittings in high magnetic fields.
Till F M Andlauer - One of the best experts on this subject based on the ideXlab platform.
-
full band Envelope Function approach for type ii broken gap superlattices
Physical Review B, 2009Co-Authors: Till F M Andlauer, P VoglAbstract:We present a charge self-consistent mesoscopic electronic-structure method for type-II broken-gap superlattices that is based on the multiband k ·p Envelope-Function method. This scheme avoids the separate classification and occupation of electron and hole states that causes the standard effective-mass theory to fail once conduction- and valence-band states strongly intermix. The computational efficiency of Envelope-Function methods is maintained. Free or bound charge-carrier redistributions can be taken into account self-consistently. With this method that we term as full-band Envelope-Function approach, we calculate effective band gaps, effective masses, and optical transition energies of InAs/GaSb superlattices as a Function of the layer width. Good agreement with experiment is obtained. We also discuss semiconductor to semimetal transitions in wide layer structures. We find the charge carriers to form a two-dimensional gas of approximately massless Dirac particles at a critical layer width.
-
full band Envelope Function approach for type ii broken gap superlattices
Physical Review B, 2009Co-Authors: Till F M Andlauer, Peter VoglAbstract:We present a charge self-consistent mesoscopic electronic-structure method for type-II broken-gap superlattices that is based on the multiband $k\ensuremath{\cdot}p$ Envelope-Function method. This scheme avoids the separate classification and occupation of electron and hole states that causes the standard effective-mass theory to fail once conduction- and valence-band states strongly intermix. The computational efficiency of Envelope-Function methods is maintained. Free or bound charge-carrier redistributions can be taken into account self-consistently. With this method that we term as full-band Envelope-Function approach, we calculate effective band gaps, effective masses, and optical transition energies of InAs/GaSb superlattices as a Function of the layer width. Good agreement with experiment is obtained. We also discuss semiconductor to semimetal transitions in wide layer structures. We find the charge carriers to form a two-dimensional gas of approximately massless Dirac particles at a critical layer width.
-
gauge invariant discretization in multiband Envelope Function theory and g factors in nanowire dots
Physical Review B, 2008Co-Authors: Till F M Andlauer, Richard Morschl, P VoglAbstract:We present a gauge-invariant discretization scheme for the multiband Envelope Function approximation including strain as well as relativistic effects. Our procedure is based on Wilson's formulation of gauge theories. The magnetic field couples to the Envelope Functions via phase factors that result from spatial discretization of the gauge covariant derivative. These phase factors contain a discretized curve integral over the vector potential. In addition, the carrier's spin couples to the magnetic field via a Zeeman term. In the case of infinitesimal grid spacings, our method becomes equivalent to the minimal substitution method. Applying our procedure, we calculate the effective electron and hole $g$ tensor of InAs/InP nanowire dots and obtain excellent agreement with experimental data. We show that the correct momentum operator ordering in the Hamiltonian grossly affects the hole $g$ factors. Furthermore, we investigate the influence of strain on $g$ factors and nonlinear Zeeman splittings in high magnetic fields.
Gail J Brown - One of the best experts on this subject based on the ideXlab platform.
-
effect of interfaces and the spin orbit band on the band gaps of inas gasb superlattices beyond the standard Envelope Function approximation
Physical Review B, 2004Co-Authors: F Szmulowicz, H J Haugan, Gail J BrownAbstract:Abstract : We developed a modified 8x8 Envelope-Function approximation (EFA) formalism for the noncommon-atom (NCA) superlattices (SL's), incorporating the effect of anisotropic and other interface (IF) interactions that go beyond the standard EFA. The boundary condition in the presence of IF interactions are used to set up a secular equation (including a transfer matrix derivation) whose physical transparency makes possible a number of valuable insights (possibility of IF bound states, analytic solutions, indirect gaps, etc.). We show that the heavy-hole-spin-orbit IF coupling is very important due to the IF localization of the SO wave Function components and the ability of the IF potential to potentially bind a hole at the IF's, all of which pose convergence problems for perturbative solutions. With two adjustable parameter for the two possible IF's, we find a very good agreement between experiment and theory for the band gaps of several sets of very long-infrared and midinfrared InAs/GaSb SL's grown at several laboratories and by us. The band gaps as a Function of GaSb and InAs widths are explained in terms of variations of the HH and conduction (C) bandwidths.
-
effect of interfaces and the spin orbit band on the band gaps of inas gasb superlattices beyond the standard Envelope Function approximation
Physical Review B, 2004Co-Authors: Frank Szmulowicz, H J Haugan, Gail J BrownAbstract:We develop a modified 8 8 8 Envelope-Function approximation (EFA) formalism for the noncommon-atom (NCA) superlattices (SL's), incorporating the effect of anisotropic and other interface (IF) interactions that go beyond the standard EFA. The boundary conditions in the presence of IF interactions are used to set up a secular equation (including a transfer matrix derivation) whose physical transparency makes possible a number of valuable insights (possibility of IF bound states, analytic solutions, indirect gaps, etc.). We show that the heavy-hole-spin-orbit IF coupling is very important due to the IF localization of the SO wave Function components and the ability of the IF potential to potentially bind a hole at the IF's, all of which pose convergence problems for perturbative solutions. With two adjustable parameter for the two possible IF's, we find a very good agreement between experiment and theory for the band gaps of several sets of very long-infrared and midinfrared InAs/GaSb SL's grown at several laboratories and by us. The band gaps as a Function of GaSb and InAs widths are explained in terms of variations of the HH and conduction (C) band bandwidths. We show that the cut-off wavelengths can be reduced by increasing the GaSb layer width. Thus, a consistent application of the EFA method with the inclusion of well established IF effects can provide useful physical insights and possesses good predictive capacity in the design of NCA SL's.
-
effect of interfaces and the spin orbit band on the band gaps of inas gasb superlattices beyond the standard Envelope Function approximation
Physical Review B, 2004Co-Authors: F Szmulowicz, H J Haugan, Gail J BrownAbstract:We develop a modified $8\ifmmode\times\else\texttimes\fi{}8$ Envelope-Function approximation (EFA) formalism for the noncommon-atom (NCA) superlattices (SL's), incorporating the effect of anisotropic and other interface (IF) interactions that go beyond the standard EFA. The boundary conditions in the presence of IF interactions are used to set up a secular equation (including a transfer matrix derivation) whose physical transparency makes possible a number of valuable insights (possibility of IF bound states, analytic solutions, indirect gaps, etc.). We show that the heavy-hole--spin-orbit IF coupling is very important due to the IF localization of the SO wave Function components and the ability of the IF potential to potentially bind a hole at the IF's, all of which pose convergence problems for perturbative solutions. With two adjustable parameter for the two possible IF's, we find a very good agreement between experiment and theory for the band gaps of several sets of very long-infrared and midinfrared InAs/GaSb SL's grown at several laboratories and by us. The band gaps as a Function of GaSb and InAs widths are explained in terms of variations of the HH and conduction (C) band bandwidths. We show that the cut-off wavelengths can be reduced by increasing the GaSb layer width. Thus, a consistent application of the EFA method with the inclusion of well established IF effects can provide useful physical insights and possesses good predictive capacity in the design of NCA SL's.
Bart Soree - One of the best experts on this subject based on the ideXlab platform.
-
self consistent procedure including Envelope Function normalization for full zone schrodinger poisson problems with transmitting boundary conditions
Journal of Applied Physics, 2018Co-Authors: Devin Verreck, Anne S Verhulst, Maarten L Van De Put, Bart Soree, Wim Magnus, N Collaert, Anda Mocuta, G GroesenekenAbstract:In the quantum mechanical simulation of exploratory semiconductor devices, continuum methods based on a k ⋅p/Envelope Function model have the potential to significantly reduce the computational burden compared to prevalent atomistic methods. However, full-zone k ⋅p/Envelope Function simulation approaches are scarce and existing implementations are not self-consistent with the calculation of the electrostatic potential due to the lack of a stable procedure and a proper normalization of the multi-band Envelope Functions. Here, we therefore present a self-consistent procedure based on a full-zone spectral k ⋅p/Envelope Function band structure model. First, we develop a proper normalization for the multi-band Envelope Functions in the presence of transmitting boundary conditions. This enables the calculation of the free carrier densities. Next, we construct a procedure to obtain self-consistency of the carrier densities with the electrostatic potential. This procedure is stabilized with an adaptive scheme that relies on the solution of Poisson’s equation in the Gummel form, combined with successive underrelaxation. Finally, we apply our procedure to homostructure In 0.53Ga 0.47As tunnel field-effect transistors (TFETs) and staggered heterostructure GaAs 0.5Sb 0.5/In 0.53Ga 0.47As TFETs and show the importance of self-consistency on the device predictions for scaled dimensions.In the quantum mechanical simulation of exploratory semiconductor devices, continuum methods based on a k ⋅p/Envelope Function model have the potential to significantly reduce the computational burden compared to prevalent atomistic methods. However, full-zone k ⋅p/Envelope Function simulation approaches are scarce and existing implementations are not self-consistent with the calculation of the electrostatic potential due to the lack of a stable procedure and a proper normalization of the multi-band Envelope Functions. Here, we therefore present a self-consistent procedure based on a full-zone spectral k ⋅p/Envelope Function band structure model. First, we develop a proper normalization for the multi-band Envelope Functions in the presence of transmitting boundary conditions. This enables the calculation of the free carrier densities. Next, we construct a procedure to obtain self-consistency of the carrier densities with the electrostatic potential. This procedure is stabilized with an adaptive scheme ...
-
full zone spectral Envelope Function formalism for the optimization of line and point tunnel field effect transistors
Journal of Applied Physics, 2015Co-Authors: Devin Verreck, Anne S Verhulst, Maarten L Van De Put, Bart Soree, Wim Magnus, Anda Mocuta, N CollaertAbstract:Efficient quantum mechanical simulation of tunnel field-effect transistors (TFETs) is indispensable to allow for an optimal configuration identification. We therefore present a full-zone 15-band quantum mechanical solver based on the Envelope Function formalism and employing a spectral method to reduce computational complexity and handle spurious solutions. We demonstrate the versatility of the solver by simulating a 40 nm wide In0.53Ga0.47As lineTFET and comparing it to p-n-i-n configurations with various pocket and body thicknesses. We find that the lineTFET performance is not degraded compared to semi-classical simulations. Furthermore, we show that a suitably optimized p-n-i-n TFET can obtain similar performance to the lineTFET.
-
15 band spectral Envelope Function formalism applied to broken gap tunnel field effect transistors
International Workshop on Computational Electronics, 2015Co-Authors: Devin Verreck, Anne S Verhulst, Bart Soree, Wim Magnus, M Van De Put, A Dabral, Aaron Thean, G GroesenekenAbstract:A carefully chosen heterostructure can significantly boost the performance of tunnel fieldeffect transistors (TFET). Modelling of these hetero- TFETs requires a quantum mechanical (QM) approach with an accurate band structure to allow for a correct description of band-to-band-tunneling. We have therefore developed a fully QM 2D solver, combining for the first time a full zone 15-band Envelope Function formalism with a spectral approach, including a heterostructure basis set transformation. Simulations of GaSb/InAs broken gap TFETs illustrate the wide body capabilities and transparant transmission analysis of the formalism.
Wim Magnus - One of the best experts on this subject based on the ideXlab platform.
-
self consistent procedure including Envelope Function normalization for full zone schrodinger poisson problems with transmitting boundary conditions
Journal of Applied Physics, 2018Co-Authors: Devin Verreck, Anne S Verhulst, Maarten L Van De Put, Bart Soree, Wim Magnus, N Collaert, Anda Mocuta, G GroesenekenAbstract:In the quantum mechanical simulation of exploratory semiconductor devices, continuum methods based on a k ⋅p/Envelope Function model have the potential to significantly reduce the computational burden compared to prevalent atomistic methods. However, full-zone k ⋅p/Envelope Function simulation approaches are scarce and existing implementations are not self-consistent with the calculation of the electrostatic potential due to the lack of a stable procedure and a proper normalization of the multi-band Envelope Functions. Here, we therefore present a self-consistent procedure based on a full-zone spectral k ⋅p/Envelope Function band structure model. First, we develop a proper normalization for the multi-band Envelope Functions in the presence of transmitting boundary conditions. This enables the calculation of the free carrier densities. Next, we construct a procedure to obtain self-consistency of the carrier densities with the electrostatic potential. This procedure is stabilized with an adaptive scheme that relies on the solution of Poisson’s equation in the Gummel form, combined with successive underrelaxation. Finally, we apply our procedure to homostructure In 0.53Ga 0.47As tunnel field-effect transistors (TFETs) and staggered heterostructure GaAs 0.5Sb 0.5/In 0.53Ga 0.47As TFETs and show the importance of self-consistency on the device predictions for scaled dimensions.In the quantum mechanical simulation of exploratory semiconductor devices, continuum methods based on a k ⋅p/Envelope Function model have the potential to significantly reduce the computational burden compared to prevalent atomistic methods. However, full-zone k ⋅p/Envelope Function simulation approaches are scarce and existing implementations are not self-consistent with the calculation of the electrostatic potential due to the lack of a stable procedure and a proper normalization of the multi-band Envelope Functions. Here, we therefore present a self-consistent procedure based on a full-zone spectral k ⋅p/Envelope Function band structure model. First, we develop a proper normalization for the multi-band Envelope Functions in the presence of transmitting boundary conditions. This enables the calculation of the free carrier densities. Next, we construct a procedure to obtain self-consistency of the carrier densities with the electrostatic potential. This procedure is stabilized with an adaptive scheme ...
-
full zone spectral Envelope Function formalism for the optimization of line and point tunnel field effect transistors
Journal of Applied Physics, 2015Co-Authors: Devin Verreck, Anne S Verhulst, Maarten L Van De Put, Bart Soree, Wim Magnus, Anda Mocuta, N CollaertAbstract:Efficient quantum mechanical simulation of tunnel field-effect transistors (TFETs) is indispensable to allow for an optimal configuration identification. We therefore present a full-zone 15-band quantum mechanical solver based on the Envelope Function formalism and employing a spectral method to reduce computational complexity and handle spurious solutions. We demonstrate the versatility of the solver by simulating a 40 nm wide In0.53Ga0.47As lineTFET and comparing it to p-n-i-n configurations with various pocket and body thicknesses. We find that the lineTFET performance is not degraded compared to semi-classical simulations. Furthermore, we show that a suitably optimized p-n-i-n TFET can obtain similar performance to the lineTFET.
-
15 band spectral Envelope Function formalism applied to broken gap tunnel field effect transistors
International Workshop on Computational Electronics, 2015Co-Authors: Devin Verreck, Anne S Verhulst, Bart Soree, Wim Magnus, M Van De Put, A Dabral, Aaron Thean, G GroesenekenAbstract:A carefully chosen heterostructure can significantly boost the performance of tunnel fieldeffect transistors (TFET). Modelling of these hetero- TFETs requires a quantum mechanical (QM) approach with an accurate band structure to allow for a correct description of band-to-band-tunneling. We have therefore developed a fully QM 2D solver, combining for the first time a full zone 15-band Envelope Function formalism with a spectral approach, including a heterostructure basis set transformation. Simulations of GaSb/InAs broken gap TFETs illustrate the wide body capabilities and transparant transmission analysis of the formalism.