Quantum-well Wires Research Articles

Dependence temperature on effective mass and susceptibility in quantum well-wires

In this study, we investigated the simulation impact of carrier density and temperature on properties such as susceptibility and effective mass of electrons in GaAs/Al x Ga1−x As quantum-well wires, involving the treatment of Coulomb interaction and the interaction between electrons and holes with longitudinal optical phonons (LO-phonon) on an equal basis. The susceptibility and effective mass were calculated and compared with the results when no phonon coupling was considered. Furthermore, the key findings were compared with results from the sum-rule version of the Singwi-Tosi-Land-Sj ö lander (STLS) theory, mean-spherical approximation (MSA) theory, and there is a high level of concordance between this formula and experimental values obtained by other researchers. Our results reveal that carrier concentration and temperature significantly affect susceptibility and effective mass of the quantum well-wires in both cases, with LO-phonon contributions. These results contribute to illuminating how Coulomb interactions and exchange-correlation energies influence the susceptibility and effective mass of GaAs/Al x Ga1−x As across a broad range of temperature and carrier density conditions.

Theoretical study of susceptibility and effective mass in semiconductor quantum well-wires

The susceptibility and effective mass of electrons and hole vary as functions of carrier density and temperature in parabolic lateral barrier quantum-well wires (QWWRs). To investigate these properties, we utilize the leading-order dynamically screened Coulomb interaction, wherein the electron self-energy is calculated within the plasmon-pole approximation (PPA). All findings for GaAs QWWRs reveal a substantial difference between susceptibility and effective mass at low and high temperatures for varying carrier densities. These results contribute to illuminate of how Coulomb interactions and exchange–correlation energies influence the susceptibility and effective mass of GaAs semiconductors across a broad range of temperature and carrier density conditions.

Helium like impurity in CdTe/ Cd1-xMnxTe semimagnetic semiconductors under magnetic field: Dimensionality effect on electron – Electron interaction

We study the effect of magnetic field on the Coulomb interaction between the two electrons confined inside a CdTe/Cd1-xMnxTe Quantum Well (QW), Quantum Well Wire (QWW) and Quantum Dot (QD) for the composition of Mn2+ ion, x = 0.3. The two particle Schrodinger equation has been solved using variational technique in the effective mass approximation. The results show that the applied magnetic field tremendously alters the Coulomb interaction of the electrons and their binding to the donor impurity by shrinking the spatial extension of the two particle wavefunction and leads to tunnelling through the barrier. The qualitative phenomenon involved in such variation of electron – electron interaction with the magnetic field has also been explained through the 3D – plot of the probability density function.

Doping-induced stability in vanadium-doped ZnO quantum well wires (QWW): Combination of DFT calculations within experimental measurements

ZnO quantum well wires (QWW) have grown on glass substrates by an inexpensive, simplified and enhanced spray pyrolysis technique then doped by Vanadium. The effects of V-doping on the structural, morphological and optical properties of the QWW were investigated experimentally and theoretically. The accuracy of control can be achieved on functional performance by adjusting vanadium doping extent. The incorporation of Vanadium in ZnO-QWW induced the formation of band tailing in states. The interactions with phonons and the presence of a tail absorption profile are following the empirical Urbach law. The electronic structure using density functional theory have shown the changes induced by vanadium doping in ZnO-QWW, where the phonon band structure and density of states were reported. The DFT results showed a good agreement with the lattice compatibility theory as well as with the experimental results.

Effect of Γ-X band mixing on the donor binding energy in a Quantum Wire

To invoke the technological applications of heterostructure semiconductors like Quantum Well (QW), Quantum Well Wire (QWW) and Quantum Dot (QD), it is important to understand the property of impurity energy which is responsible for the peculiar electronic & optical behavior of the Low Dimensional Semiconductor Systems (LDSS). Application of hydrostatic pressure P>35kbar drastically alters the band offsets leading to the crossover of Γ band of the well & X band of the barrier resulting in an indirect transition of the carrier and this effect has been studied experimentally and theoretically in a QW structure. In this paper, we have investigated the effect of Γ-X band mixing due to the application of hydrostatic pressure in a GaAs/AlxGa1-xAs QWW system. The results are presented and discussed for various widths of the wire.

Polaronic effects on the collective excitation in a GaAs parabolic quantum wire

In this paper, the plasmon-longitudinal optical (LO) phonon interaction effects on the intrasubband structure factor, on the pair correlation function and on the intrasubband plasmon energy associated with the lowest subband in a GaAs parabolic quantum well wire (QWW) are investigated by varying the subband separation energy and the electronic density. The calculations are performed using the self-consistent field approximation, which includes the local-field correction within the Singwi, Tosi, Land and Sjölander (STLS) theory, at zero temperature and assuming a three-subband model where only the first subband is occupied by electrons. The theoretical results obtained via STLS theory are compared with the random phase approximation (RPA) approach results, in order to emphasize the importance of the local field corrections (LFC) for the calculation of the collective excitations in quasi-one-dimensional systems.

Lowest Excited-State Impurity Binding Energy in InGaN/GaN Parabolic QWW: Magnetic Field Effect

In this paper, we have investigated the magnetic field effect on the lowest excited-state binding energy of hydrogenic shallow-donor impurity in wurtzite (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) using the finite-difference method within the quasi-one-dimensional effective potential model. The calculations are performed within the framework of the effective mass approximation. A cylindrical QWW effective radius is taken into account to describe the lateral confinement strength. The numerical results show that: (i) the probability density is the largest on a circularity whose radius is the effective radius and (ii) the lowest excited-state binding energy is the largest when an impurity is located on this circularity while it starts to decrease as the impurity is away from the circularity.

Impurity-related linear and nonlinear optical response in quantum-well wires with triangular cross section

The 1s-like and 2p-like donor impurity energy states are studied in a semiconductor quantum wire of equilateral triangular cross section as functions of the impurity position and the geometrical size of the structure. Linear and nonlinear coefficients for the optical absorption and relative refractive index change associated with 1s→2p transitions are calculated for both the x-polarization and y-polarization of the incident light. The results show a mixed effect of redshift and blueshift depending on the location of the donor atom. Also, strong nonlinear contributions to the optical absorption coefficient are obtained for both polarizations in the on-center impurity case.

Magnetic field effect on the ground-state binding energy in InGaN/GaN parabolic QWW

Within the framework of the effective mass scheme, the ground-state binding energy of hydrogenic shallow-donor impurity in wurtzite (WZ) (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) subjected to magnetic field is investigated. The finite-difference method within the quasi-one-dimensional effective potential model is used. A cylindrical QWW effective radius is introduced to describe the lateral confinement strength. The results show that: (i) the binding energy is the largest for the impurity located at a point corresponding to the largest electron probability density and (ii) it increases with increasing external magnetic field.

New wavefunctions for the excited states of an axial impurity in a quantum wire

The binding energy of a central hydrogenic impurity located in a finite confining potential quantum well wire (QWW) has been calculated within the effective mass approximation. The study is devoted to deal with the first four excited states (2P±, 2Pz and 2s) in the presence of a uniform axial magnetic field. The different effective masses of the wire and barrier are taken into consideration. New forms of the trial variational wavefunctions have been introduced. These forms are analogous to the new form given in our earlier work on the ground state (1s). They are distinct from the conventional forms by the fact that they satisfy the required boundary conditions in the case of different masses of wire and barrier. The resulting new expressions for the energy and binding energy of the four excited states have led to more accurate results for the binding energy and have improved considerably its values. It is also of importance to point out that a new iteration technique has been introduced to perform the minimization procedure for the energy of the state (2s). This technique may be applied in similar problems of slow convergence.

Stark effect-dependent of ground-state donor binding energy in InGaN/GaN parabolic QWW

Using the finite-difference method within the quasi-one-dimensional effective potential model and effective mass approximation, the ground-state binding energy of hydrogenic shallow-donor impurity in wurtzite (WZ) (In,Ga)N/GaN parabolic transversal-section quantum-well wires (PQWWs) subjected to external electric field is investigated. An effective radius of a cylindrical QWW describing the strength of the lateral confinement is introduced. The results show that (i) the position of the largest electron probability density in x–y plane is located at a point and it is pushed along the negative sense by the electric field directed along the positive sense, (ii) the ground-state binding energy is largest for the impurity located at this point and starts to decrease when the impurity is away from this point, (iii) the ground-state binding energy decreases with increase in the external electric field and effective radius, and (iv) the Stark-shift increases with the increase of the external electric field and the effective radius.

One phonon-assisted electron Raman scattering in a wurtzite cylindrical quantum well wire

We report the electron resonant Raman scattering (ERRS) process related to the longitudinal optical (LO), interface optical (IO) and quasi-confined (QC) phonons in a cylindrical GaN–AlN quantum well wire (QWW). We present the differential cross-section (DCS) and study the selection rules. Results reveal that the emitted photon frequency decreases with increasing the radius because of the size-selective Raman scattering effect and the built-in electric field. The contribution to the DCS mainly stems from the GaN-type LO (LO1), QC and IO phonons when the wire is thin, but the LO1 and QC phonons are dominant for the thick wire.

Exciton in an anisotropic parabolic quantum-well wire in the presence of a magnetic field

The properties of an exciton in an anisotropic parabolic quantum-well wire in a magnetic field are investigated theoretically. It is found that a decrease in the confinement length increases the exciton binding energy and decreases the longitudinal extension of the exciton wave function. The results of the exciton diamagnetic shifts are in agreement with previously reported magneto-photoluminescence experimental data. Details of the effects of the magnetic field on the binding energy and the wave function of the exciton have been investigated. The conclusion is drawn that the magnetic field has a more pronounced effect in wider quantum-well wires.

Charged excitons in parabolic quantum-well wires under magnetic filed

The binding energies of the charged excitons(negative X- and positive X+ excitons) are calculated using the finite-difference method within the quasi-one-dimensional effective potential model. The effects due to the magnetic filed and quantum confinements on the binding energy are analyzed, and the following results are obtained:(1) relative electron and hole harmonic oscillator confinement each have a strong effect on the stablity of charged excitons, the binding energy of X+ is not always larger than that of X-, e.g., due to the increase of the hole harmonic oscillator length, leading to the crossing of X+ and X- lines as recently observed experimentally;(2) the magnetic field leads to an increase of the binding energy, and the magnetic field dependence of the binding energy is related to the harmonic oscillator length.

Simultaneous effects of hydrostatic pressure and electric field on impurity binding energy and polarizability in coupled InAs/GaAs quantum wires

This work is concerned with the theoretical study of the combined effects of applied electric field and hydrostatic pressure on the binding energy and impurity polarizability of a donor impurity in laterally coupled double InAs/GaAs quantum-well wires. Calculations have been made in the effective mass and parabolic band approximations and using a variational method. The results are reported for different configurations of wire and barriers widths, impurity position, and electric field and hydrostatic pressure strengths. Our results show that for symmetrical structures the binding energy is an even function of the impurity position along the growth direction of the structure. Also, we found that for hydrostatic pressure strength up to 38 kbar, the binding energy increases linearly with hydrostatic pressure, while for larger values of hydrostatic pressure the binding energy has a non-linear behavior. Finally, we found that the hydrostatic pressure can increase the coupling between the two parallel quantum-well wires.

Correlation effects for a quasi‐one‐dimensional polaron gas

AbstractIn this work, we investigate the plasmon–LO phonon interaction effects on the intrasubband structure factor, electron–electron effective potential, and plasmon energy associated with the lowest subband in a GaAs‐AlGaAs rectangular quantum‐well wire (QWW) as a function of the electronic density. Our calculations are performed using the self‐consistent field approximation, which includes the local‐field correction (LFC) within the Singwi, Tosi, Land, and Sjolander (STLS) theory, at zero temperature and assuming a three‐subband model, where only the first subband is occupied by electrons. We report for the first time dips in the structure factor spectra as a function of the quasi‐one‐dimensional (Q1D) plasmon–LO phonon wavevector that are directly related with the resonant split of the collective excitation energy into two branches due to the polaronic effects.

EXTERNAL ELECTRIC FIELD EFFECT ON THE HYDROGENIC DONOR IMPURITY IN ZINC-BLENDE GaN/AlGaN CYLINDRICAL QUANTUM WELL WIRE

The binding energy of a hydrogenic donor impurity in a zinc-blende GaN / AlGaN cylindrical quantum well wire (QWW) is calculated in the framework of effective-mass envelope-function theory using the plane wave basis. It is shown that the donor binding energy is highly dependent on the impurity position, the radius of the wire and the external electric field. In addition, Stark shift dependence on the radius of the QWW and the external electric field is also calculated. The donor binding energy has a maximum when the impurity is located at the center of the QWW. The donor binding energy decreases with the increase of the external electric field, but stark shift increases with the increase of the external electric field or the radius of the QWW.

External electric field effect on the hydrogenic donor impurity in zinc-blende InGaN/GaN cylindrical quantum well wire

The binding energy of a hydrogenic donor impurity in a zinc-blende InGaN/GaN cylindrical quantum well wire (QWW) is calculated in the framework of effective-mass envelope-function theory using the plane wave basis. It is shown that the donor binding energy is highly dependent on impurity position, radius of the wire, and external electric field. In addition, Stark shift dependence on radius of the QWW and external electric field is also calculated. The donor binding energy has a maximum when the impurity is located on the axis of the QWW. The donor binding energy decreases with increase in the external electric field, while Stark shift increases with increase in the external electric field or radius of the QWW.

Combined effects of hydrostatic pressure and electric field on the donor binding energy and polarizability in laterally coupled double InAs/GaAs quantum-well wires

This work is concerned with the theoretical study of the combined effects of applied electric field and hydrostatic pressure on the binding energy and impurity polarizability of a donor impurity in laterally coupled double InAs/GaAs quantum-well wires. calculations have been made in the effective mass and parabolic band approximations and using a variational method. The results are reported for different configurations of wire and barriers widths, impurity position, and electric field and hydrostatic pressure strengths. Our results show that for symmetrical structures the binding energy is an even function of the impurity position along the growth direction of the structure. Also, we found that for hydrostatic pressure strength up to 38 kbar, the binding energy increases linearly with hydrostatic pressure, while for larger values of hydrostatic pressure the binding energy has a nonlinear behavior. Finally, we found that the hydrostatic pressure can increase the coupling between the two parallel quantum well wires.

Donor in cylindrical quantum well wire under the action of an applied magnetic field

In this paper we present a calculation of the binding energy of a donor impurity in a cylindrical GaAs-Ga 0.6Al 0.4As quantum well wire (QWW) as a function of an applied magnetic field for different wire radii and different positions of the donor. The model considers an infinite length QWW with a carrier that is confined laterally by a parabolic potential and the presence of a uniform magnetic field applied parallel to the wire axis. The 1s-like impurity state is considered using the effective-mass approximation within the variational approach. We found that for a given wire radius the binding energy of the impurity increases with the magnetic field and that for a given magnetic field value it decreases with wire radius. Our results are in good agreement with previous theoretical reports.