Ah Sa - Academia.edu (original) (raw)

Papers by Ah Sa

Research paper thumbnail of Bound polaron in spherical quantum dots

ABSTRACT Using a variational calculation within the effective mass approximation, we calculate th... more ABSTRACT Using a variational calculation within the effective mass approximation, we calculate the binding energy of a bound polaron to shallow donor impurity in spherical Quantums dots (QD) . The interactions of carrier charges (electron and ion) with the longitudinal optical phonons as well as the surface optical phonons are considered. Calculations are made using a finite confinement potential. Results are obtained as a function of the dot size and the donor impurity position. It is found that the binding energy is very sensitive to the polaronic effect, the confinement and the impurity position.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

physica status solidi (b), 1999

ABSTRACT Available from http://www3.interscience.wiley.com/cgi-bin/abstract/40003582/START

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

ABSTRACT Within the effective-mass approximation, we have investigated the influence of a strong ... more ABSTRACT Within the effective-mass approximation, we have investigated the influence of a strong magnetic field on the ground state binding energy and the photon energy dependence of the photoionization cross-section of a shallow donor impurity in a quasi-one-dimensional rectangular quantum wire with infinite and finite potential barriers, using a variational approach. It is found that the binding energy and the photoionization cross-section as a function of photon energy were drastically dependent on the sizes of the wire, the potential well heights and the applied magnetic field.

Research paper thumbnail of The effect of the electron-longitudinal optical phonons interaction on the photoionization in a quantum well

Journal of Physics and Chemistry of Solids, 1998

Research paper thumbnail of The Photoionization Cross-Section of Impurities in Quantum Dots

physica status solidi (b), 2002

ABSTRACT In quantum dot structures, photoionization has been considered as an optical transition ... more ABSTRACT In quantum dot structures, photoionization has been considered as an optical transition from the impurity ground state to the conduction subbands. Using a variational approach, we have calculated the photon energy dependence of the photoionization cross-section for a hydrogenic donor impurity in an infinite barrier GaAs quantum dot as a function of the sizes of the dot and the impurity position. The results we have obtained show that the photoionization cross-section is strongly affected by the quantum size effects and the position of the impurity and its overall shape seems to be a signature of the quantum dot system.

Research paper thumbnail of The finite element simulation for the shallow impurity in quantum dots

Research paper thumbnail of Electron-confined longitudinal optical phonon interaction and strong magnetic field effects on the binding energy in GaAs quantum wells

Journal of Applied Physics, 2002

ABSTRACT We study the ground state binding energy of a hydrogenic impurity subjected to an extern... more ABSTRACT We study the ground state binding energy of a hydrogenic impurity subjected to an external strong magnetic field taking into account the interaction of the electron with confined longitudinal optical phonon in GaAs/Ga1-xAlxAs quantum wells. Calculations are performed within the effective mass approximation using the Lee-Low-Pines [Phys. Rev. 90, 297 (1953)] variational method and considering the infinite and finite character of the barrier potential. The binding energy is calculated as a function of the magnetic field and the well size. The results we have obtained show that the binding energies are very sensitive to the combined effect of the well size, the strong applied magnetic field, and the electron-phonon interaction.

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

ABSTRACT The effect of a strong magnetic field on the binding energy and the photon energy depend... more ABSTRACT The effect of a strong magnetic field on the binding energy and the photon energy dependence of the photoionization cross-section as a function of the well size is studied in a quantum well for several values of the magnetic field, taking into account the finite character of the barrier potential. The results we have obtained show that the applied strong magnetic field affects drastically the binding energy and the photoionization cross-section and this effect is more significant in a quasi-two-dimensional structure than in a three-dimensional system.

Research paper thumbnail of Photoionization of shallow donor impurities in finite-barrier quantum wells

The dependence of the photoionization cross-section on photon energy is calculated for shallow do... more The dependence of the photoionization cross-section on photon energy is calculated for shallow donors in finite-barrier GaAs/Ga(1-x)Al(x)As quantum well as well as the binding energy as a function of well width. The effect of magnetic field is also considered.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

physica status solidi (b), 1999

ABSTRACT Available from http://www3.interscience.wiley.com/cgi-bin/abstract/40003582/START

Research paper thumbnail of The Photoionization Cross-Section of Impurities in Quantum Dots

In quantum dot structures, photoionization has been considered as an optical transition from the ... more In quantum dot structures, photoionization has been considered as an optical transition from the impurity ground state to the conduction subbands. Using a variational approach, we have calculated the photon energy dependence of the photoionization cross-section for a hydrogenic donor
impurity in an infinite barrier GaAs quantum dot as a function of the sizes of the dot and the impurity position. The results we have obtained show that the photoionization cross-section is strongly affected by the quantum size effects and the position of the impurity and its overall shape seems to be a signature of the quantum dot system.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

Physica Status Solidi B-basic Solid State Physics, 1999

The photon energy dependence of the photoionization cross-section is calculated for a hydrogenic ... more The photon energy dependence of the photoionization cross-section is calculated for a hydrogenic shallow donor impurity located in quantum-well wires of GaAs, surrounded by Ga 1Àx Al x As as a function of the sizes of the wire for both infinite-and finite-well models. The results show that the photoionization cross-section depends on the polarization axis relative to the wire axis as well as on the quantum wire dimensions and the inhomogeneous confinement potential.

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

Within the effective-mass approximation, we have investigated the in¯uence of a strong magnetic ®... more Within the effective-mass approximation, we have investigated the in¯uence of a strong magnetic ®eld on the ground state binding energy and the photon energy dependence of the photoionization cross-section of a shallow donor impurity in a quasi-one-dimensional rectangular quantum wire with in®nite and ®nite potential barriers, using a variational approach. It is found that the binding energy and the photoionization cross-section as a function of photon energy were drastically dependent on the sizes of the wire, the potential well heights and the applied magnetic ®eld. q

Research paper thumbnail of The effect of the electron-longitudinal optical phonons interaction on the photoionization in a quantum well

Journal of Physics and Chemistry of Solids, 1998

Using variational technique, we have calculated the photon energy dependence of the photoionizati... more Using variational technique, we have calculated the photon energy dependence of the photoionization cross-section and the binding energy of a hydrogenic donor impurity in infinite-barrier quantum well (QW) as a function of well width, taking into account the interaction between electron and bulk longitudinal-optical (LO) phonons. The initial ground state and the final subband state wave functions are described, respectively, within the framework of the strong coupling treatment of the polaron theory and in the Lee-Low-Pines approximation. The results indicate that the effects of the electron-LO phonon coupling on the binding energy and the spectral dependence of the cross-section are very significant.

Research paper thumbnail of Bound polaron in spherical quantum dots

ABSTRACT Using a variational calculation within the effective mass approximation, we calculate th... more ABSTRACT Using a variational calculation within the effective mass approximation, we calculate the binding energy of a bound polaron to shallow donor impurity in spherical Quantums dots (QD) . The interactions of carrier charges (electron and ion) with the longitudinal optical phonons as well as the surface optical phonons are considered. Calculations are made using a finite confinement potential. Results are obtained as a function of the dot size and the donor impurity position. It is found that the binding energy is very sensitive to the polaronic effect, the confinement and the impurity position.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

physica status solidi (b), 1999

ABSTRACT Available from http://www3.interscience.wiley.com/cgi-bin/abstract/40003582/START

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

ABSTRACT Within the effective-mass approximation, we have investigated the influence of a strong ... more ABSTRACT Within the effective-mass approximation, we have investigated the influence of a strong magnetic field on the ground state binding energy and the photon energy dependence of the photoionization cross-section of a shallow donor impurity in a quasi-one-dimensional rectangular quantum wire with infinite and finite potential barriers, using a variational approach. It is found that the binding energy and the photoionization cross-section as a function of photon energy were drastically dependent on the sizes of the wire, the potential well heights and the applied magnetic field.

Research paper thumbnail of The effect of the electron-longitudinal optical phonons interaction on the photoionization in a quantum well

Journal of Physics and Chemistry of Solids, 1998

Research paper thumbnail of The Photoionization Cross-Section of Impurities in Quantum Dots

physica status solidi (b), 2002

ABSTRACT In quantum dot structures, photoionization has been considered as an optical transition ... more ABSTRACT In quantum dot structures, photoionization has been considered as an optical transition from the impurity ground state to the conduction subbands. Using a variational approach, we have calculated the photon energy dependence of the photoionization cross-section for a hydrogenic donor impurity in an infinite barrier GaAs quantum dot as a function of the sizes of the dot and the impurity position. The results we have obtained show that the photoionization cross-section is strongly affected by the quantum size effects and the position of the impurity and its overall shape seems to be a signature of the quantum dot system.

Research paper thumbnail of The finite element simulation for the shallow impurity in quantum dots

Research paper thumbnail of Electron-confined longitudinal optical phonon interaction and strong magnetic field effects on the binding energy in GaAs quantum wells

Journal of Applied Physics, 2002

ABSTRACT We study the ground state binding energy of a hydrogenic impurity subjected to an extern... more ABSTRACT We study the ground state binding energy of a hydrogenic impurity subjected to an external strong magnetic field taking into account the interaction of the electron with confined longitudinal optical phonon in GaAs/Ga1-xAlxAs quantum wells. Calculations are performed within the effective mass approximation using the Lee-Low-Pines [Phys. Rev. 90, 297 (1953)] variational method and considering the infinite and finite character of the barrier potential. The binding energy is calculated as a function of the magnetic field and the well size. The results we have obtained show that the binding energies are very sensitive to the combined effect of the well size, the strong applied magnetic field, and the electron-phonon interaction.

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

ABSTRACT The effect of a strong magnetic field on the binding energy and the photon energy depend... more ABSTRACT The effect of a strong magnetic field on the binding energy and the photon energy dependence of the photoionization cross-section as a function of the well size is studied in a quantum well for several values of the magnetic field, taking into account the finite character of the barrier potential. The results we have obtained show that the applied strong magnetic field affects drastically the binding energy and the photoionization cross-section and this effect is more significant in a quasi-two-dimensional structure than in a three-dimensional system.

Research paper thumbnail of Photoionization of shallow donor impurities in finite-barrier quantum wells

The dependence of the photoionization cross-section on photon energy is calculated for shallow do... more The dependence of the photoionization cross-section on photon energy is calculated for shallow donors in finite-barrier GaAs/Ga(1-x)Al(x)As quantum well as well as the binding energy as a function of well width. The effect of magnetic field is also considered.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

physica status solidi (b), 1999

ABSTRACT Available from http://www3.interscience.wiley.com/cgi-bin/abstract/40003582/START

Research paper thumbnail of The Photoionization Cross-Section of Impurities in Quantum Dots

In quantum dot structures, photoionization has been considered as an optical transition from the ... more In quantum dot structures, photoionization has been considered as an optical transition from the impurity ground state to the conduction subbands. Using a variational approach, we have calculated the photon energy dependence of the photoionization cross-section for a hydrogenic donor
impurity in an infinite barrier GaAs quantum dot as a function of the sizes of the dot and the impurity position. The results we have obtained show that the photoionization cross-section is strongly affected by the quantum size effects and the position of the impurity and its overall shape seems to be a signature of the quantum dot system.

Research paper thumbnail of Photoionization of Impurities in Quantum-Well Wires

Physica Status Solidi B-basic Solid State Physics, 1999

The photon energy dependence of the photoionization cross-section is calculated for a hydrogenic ... more The photon energy dependence of the photoionization cross-section is calculated for a hydrogenic shallow donor impurity located in quantum-well wires of GaAs, surrounded by Ga 1Àx Al x As as a function of the sizes of the wire for both infinite-and finite-well models. The results show that the photoionization cross-section depends on the polarization axis relative to the wire axis as well as on the quantum wire dimensions and the inhomogeneous confinement potential.

Research paper thumbnail of The effect of a strong magnetic field on the binding energy and the photoionization process in quantum-well wires

Journal of Physics and Chemistry of Solids, 2003

Within the effective-mass approximation, we have investigated the in¯uence of a strong magnetic ®... more Within the effective-mass approximation, we have investigated the in¯uence of a strong magnetic ®eld on the ground state binding energy and the photon energy dependence of the photoionization cross-section of a shallow donor impurity in a quasi-one-dimensional rectangular quantum wire with in®nite and ®nite potential barriers, using a variational approach. It is found that the binding energy and the photoionization cross-section as a function of photon energy were drastically dependent on the sizes of the wire, the potential well heights and the applied magnetic ®eld. q

Research paper thumbnail of The effect of the electron-longitudinal optical phonons interaction on the photoionization in a quantum well

Journal of Physics and Chemistry of Solids, 1998

Using variational technique, we have calculated the photon energy dependence of the photoionizati... more Using variational technique, we have calculated the photon energy dependence of the photoionization cross-section and the binding energy of a hydrogenic donor impurity in infinite-barrier quantum well (QW) as a function of well width, taking into account the interaction between electron and bulk longitudinal-optical (LO) phonons. The initial ground state and the final subband state wave functions are described, respectively, within the framework of the strong coupling treatment of the polaron theory and in the Lee-Low-Pines approximation. The results indicate that the effects of the electron-LO phonon coupling on the binding energy and the spectral dependence of the cross-section are very significant.