A. Zakharova

Self-consistent modeling of the current–voltage characteristics of resonant tunneling structures with type II heterojunctions

We present a model and results of self-consistent calculation of current–voltage (I–V) characteristics of the InAs/AlSb/InAs, InAs/AlSb/GaSb resonant tunneling structures with type II heterojunctions. The different current components, charge accumulation in the quantum well and quasi-Fermi level variation in contacts and spacers due to the drift-diffusion processes, are taken into account. The kp band model is used to describe the interband and intraband tunneling processes. The transfer Hamiltonian approach is employed to obtain the resonant tunneling current density and charge density in the quantum well. A good quantitative agreement with the experiment is obtained for both structures including the agreement for the values of peak-to-valley (P/V) current ratio.

Optical absorption of polarized light in InAs/GaSb quantum wells

Using an eight-band k p model Hamiltonian with the Burt-Foreman envelope function theory, we have investigated the optical absorption of both linearly and circularly polarized light, as well as rel ...

Effects of lattice mismatch and bulk anisotropy on interband tunneling in broken-gap heterostructures

We have studied the effects of bulk anisotropy and the strain induced by lattice mismatch on the interband tunneling in broken-gap single-barrier InAs/AlSb/GaSb heterostructures and double-barrier InAs/AlSb/GaSb/InAs/AlSb/GaSb heterostructures. We have used the eight-band k.p model and the scattering matrix method, combined with the Burt envelope function theory, to calculate the interband transmission coefficients through the broken-gap heterostructures. We have found a noticeable anisotropy of the transmission coefficients when the magnitude of the in-plane wave vector increases to around 0.25 nm(-1). We have also found that the strain and the bulk anisotropy of quasiparticle dispersion produce additional peaks in the tunneling probability. For the double-barrier resonant-tunneling structures we discover a large spin splitting of the resonant-tunneling peaks caused by the lack of inversion symmetry. A strong influence of the strain induced by lattice mismatch appears in the current-voltage characteristics of the studied broken-gap heterostructures. In InAs/AlSb/GaSb structures the interband tunneling processes into the heavy-hole states contribute mainly to the peak current density if the sample is grown on InAs, but if the sample is grown on GaSb the interband tunneling processes into the light-hole states become the main contribution to the peak current density. As a result, the structure grown on GaSb has a much larger peak current density. This phenomenon was observed experimentally. (Less)

Self-consistent calculation of current-voltage characteristics of resonant tunnelling structures with type II heterojunctions

Abstract Resonant tunnelling structures (RTS) with type II heterojunctions such as InAs/AlSb/InAs RTS are investigated theoretically utilizing a self-consistent solution for potential shape and carrier density distribution. The tunnelling probability and tunnel current are calculated using the transfer matrix method and Kanes model. Band-bending is obtained, allowing for a realistic structure of spacer and contact regions. The transfer Hamiltonian approach is employed to determine the 2D charge density in the quantum well. As a result, current-voltage ( I - V ) characteristics are obtained for InAs/AlSb/InAs diodes close to those observed experimentally.

Modelling of the current-voltage characteristics of InAs/AlGaSb/GaSb double barrier diodes with interband resonant tunnelling

Previously we developed a model for InAs/AlSb/GaSb resonant tunnelling structures (RTSs) and investigated the mechanisms of peak and valley current in these diodes, which exhibit high values of peak-to-valley (P/V) current ratio. Good quantitative agreement with the experiment was achieved both for the values of peak and valley current density for the first time. Here we show that the P/V current ratio can be essentially enlarged by employing the AlGaSb material instead of AlSb. The calculated current-voltage (I-V) characteristic of the InAs/AlGaSb/GaSb RTSs with 30 and 20 A barriers and 65 A quantum well showed a P/V current ratio of about 800 at lattice temperature T = 77 K. This value is much greater than all known experimental values of P/V current ratio for RTSs until now.

Optical anisotropy of InAs/GaSb broken-gap quantum wells

We investigate in detail the optical anisotropy of absorption of linearly polarized light in InAs/GaSb quantum wells grown on GaSb along the [001] direction, which can be used as an active region of different laser structures. The energy level positions, the wave functions, the optical matrix elements, and the absorption coefficients are calculated using the eight-band k · p model and the Burt-Foreman envelope function theory. In these calculations, the Schrödinger and Poisson equations are solved self-consistently taking the lattice-mismatched strain into account. We find that a realistic Hamiltonian, which has the C2v symmetry, results in considerable anisotropy of optical matrix elements for different directions of light polarization and different directions of the initial-state in-plane wave vector, including low-symmetry directions. We trace how the optical matrix elements and absorption are modified when spin-orbit interaction and important symmetry breaking mechanisms are taken into account (structural inversion asymmetry, bulk inversion asymmetry, and interface Hamiltonian). These mechanisms result in an almost 100% anisotropy of the absorption coefficients as the light polarization vector rotates in the plane of the structure and in a plane normal to the interfaces.

Spin-related phenomena in InAs/GaSb quantum wells

We have studied theoretically the influence of symmetry breaking mechanisms: structural inversion asymmetry, bulk inversion asymmetry, relativistic and non-relativistic interface Hamiltonian and warping on spin split of levels ΔE and optical absorption of linearly polarized light in asymmetrical quantum wells made from zincblende materials grown on [001] direction. The AlSb/InAs/GaSb/AlSb broken-gap quantum wells with hybridized electron-hole states sandwiched by the AlSb barriers have been considered. We have obtained substantial contributions of these effects into the absolute values of spin split of electron and hole states and spinflip optical transitions for the initial state in-plane wave vectors along low symmetry directions such as [12].