Ahmed Sali | University of Sidi Mohammed Ben Abdellah (original) (raw)
Papers by Ahmed Sali
Using a variational calculation within the effective mass approximation, we calculate the binding... more 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.
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.
Journal of Applied Physics, 2002
The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/Mg x Zn1− ... more The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/Mg x Zn1− x O quantum well
Il Nuovo Cimento D, 1998
The effect of the electric field on the donor impurity is investigated in the case of a spherical... more The effect of the electric field on the donor impurity is investigated in the case of a spherical conduction band with the use of a variational procedure. An analytical expression for the photoionization cross-section as a function of photon energy within the effective mass approximation of an impurity atom in an applied field was obtained. The effect of central cell correction by means of a semi-empirical short-range potential is taken into account. It has been found that the binding energy and the spectral dependence of the cross-section are very sensitive to the electric field, the shape of the impurity potential and their combined effect.
Physica Status Solidi B-basic Solid State Physics, 1997
Physica Status Solidi B-basic Solid State Physics, 1996
The effect of a magnetic field on the hydrogenic shallow donor impurity is investigated with the ... more The effect of a magnetic field on the hydrogenic shallow donor impurity is investigated with the use of a variational method. Two different expressions describing the photoionization cross-section for donor-conduction band transitions are obtained both in absence and presence of an applied strong magnetic field. The effect of the strong magnetic field is well observed in a semiconducting material of high dielectric constant and low effective mass such as germanium. It has been found that the photoionization cross-section is strongly affected by the magnetic field.
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.
Physica Status Solidi B-basic Solid State Physics, 2002
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.
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.
Journal of Physics-condensed Matter, 1999
The effect of a strong magnetic field on the binding energy and the photon energy dependence of t... more 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 0953-8984/11/11/013/img9 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.
Physica Status Solidi B-basic Solid State Physics, 1997
he iffet of the iletron±vongitudinl yptil honon sntertion on the hotoioniztion in untum ell ires ... more he iffet of the iletron±vongitudinl yptil honon sntertion on the hotoioniztion in untum ell ires eF liD wF pliyou I D nd rF voumrhri h eprtement de hysiqueD pult e des ienesD fFF RHIHD wekn esD woroo @eeived epril PQD IWWTY in revised form xovemer TD IWWTA he photon energy dependene of the photoioniztion rossEsetion is lulted for shllow donors in infinite potentil quntum well wires with retngulr rossEsetions s funtion of the size of the wireF he eletron±longitudinl optil @vyA phonon intertion is tken into ount using the strong oupling tretment for the impurity stte nd the veeEvowEines vritionl tretment for the sund finl stteF he results we otined show tht the photoioniztion rossEsetion nd the optil photoioniztion threshold energy re drmtilly dependent on the sizes of the wire nd re very sensitive to the eletron±vy phonon ouplingF IF sntrodution tudies of the strutures with quntum onfinement to one dimensionD iFeFD quntum well wires @sAD in whih the eletron motion long the length of the wire is tht of qusiEfree eletron nd is quntized in the two dimensions perpendiulr to the wireD re very interesting prolems in reent yersF he presene of ionized impurities in the s nd the smll sizes of these strutures ply fundmentl role in some physil properties suh s optil nd trnsport mehnism properties t low tempertureF his role eomes inresingly importnt s the dimensions of the wire rossEsetion eome smll nd it is thus quite different from tht in the ulk seF pew theoretil nd experimentl studies exist for optil properties suh s the photoioniztion rossEseE tion in the strutures with quntum onfinement to two dimensionsF kihw et lF I hve experimentlly nd theoretilly exmined the photoioniztion of deep trps in elqesGqes multiple quntum well lyers grown y metlorgni hemilEvpor depositionF ilEid nd omk PD Q hve lulted the dependene of the photoionizE tion rossEsetion on photon energy for shllow donors in quntum wells for light polrE ized long nd perpendiulr to the growth diretion with the ssumption of n infinite onfining potentilF wore reentlyD sliwi nd ilEid R improved their lultions y using finite potentil rrierF sn the qusiEoneEdimensionl struturesD there hs een some theoretil ttempts to study the optil properties in s S to IHF o our knowledgeD the photoioniztion rossEsetion hs not yet een performed in the qusiE oneEdimensionl semiondutorsF he present pper is devoted to the study of the spetrl dependene of the photoioniE ztion rossEsetion s" hw for polron ound to shllow hydrogeni impurity in inE I iFxFFD h eprtement de hysiqueD fFF fensoud SPHTD p esD worooF eF li et lFX iffet of iletron±vy honon sntertion on hotoioniztion IRS
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
Physica B-condensed Matter, 1997
The photon energy dependence of the photoionization cross-sections are calculated for a hydrogeni... more The photon energy dependence of the photoionization cross-sections are calculated for a hydrogenic shallow impurity located in quantum-well wires of GaAs, surrounded by Gal _.Al,As as a function of the sizes of the wire for several values of the heights of the potential barriers. The results we have obtained show that the photoionization cross-sections are affected by the sizes of the wire and the height of the barrier and also that their magnitude are larger than those in comparable infinite potential quantum-well wires.
Using the finite element method, the binding energies of a hydrogenic shallow donor impurity are ... more Using the finite element method, the binding energies of a hydrogenic shallow donor impurity are investigated in a cubic GaAs/ Ga 1Àx Al x A s quantum dot structure with realistic potential barrier height under the combined effect of hydrostatic pressure and temperature in the framework of the effective mass approximation. In the calculations, we have taken into account the electronic effective mass, dielectric constant, and conduction band offset between the dot and barriers varying with pressure and temperature. The results we have obtained show that the donor binding energy varies with the dot size, the confining potential, the position of impurity, the hydrostatic pressure and temperature. It is also found that the donor binding energy increases linearly with the pressure in direct gap regime and its variation is larger for narrower dots only and drops slightly with the temperature. A good agreement is obtained with the existing literature values.
c We examine the binding energy using the finite element method in quantum dots. c Large number o... more c We examine the binding energy using the finite element method in quantum dots. c Large number of finite elements and smaller mesh size h yield best results. c Our results of the binding energy agree with those of the variational method. c Increasing the potential barrier height will increase the impurity binding energy.
Using a variational calculation within the effective mass approximation, we calculate the binding... more 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.
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.
Journal of Applied Physics, 2002
The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/Mg x Zn1− ... more The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/Mg x Zn1− x O quantum well
Il Nuovo Cimento D, 1998
The effect of the electric field on the donor impurity is investigated in the case of a spherical... more The effect of the electric field on the donor impurity is investigated in the case of a spherical conduction band with the use of a variational procedure. An analytical expression for the photoionization cross-section as a function of photon energy within the effective mass approximation of an impurity atom in an applied field was obtained. The effect of central cell correction by means of a semi-empirical short-range potential is taken into account. It has been found that the binding energy and the spectral dependence of the cross-section are very sensitive to the electric field, the shape of the impurity potential and their combined effect.
Physica Status Solidi B-basic Solid State Physics, 1997
Physica Status Solidi B-basic Solid State Physics, 1996
The effect of a magnetic field on the hydrogenic shallow donor impurity is investigated with the ... more The effect of a magnetic field on the hydrogenic shallow donor impurity is investigated with the use of a variational method. Two different expressions describing the photoionization cross-section for donor-conduction band transitions are obtained both in absence and presence of an applied strong magnetic field. The effect of the strong magnetic field is well observed in a semiconducting material of high dielectric constant and low effective mass such as germanium. It has been found that the photoionization cross-section is strongly affected by the magnetic field.
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.
Physica Status Solidi B-basic Solid State Physics, 2002
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.
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.
Journal of Physics-condensed Matter, 1999
The effect of a strong magnetic field on the binding energy and the photon energy dependence of t... more 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 0953-8984/11/11/013/img9 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.
Physica Status Solidi B-basic Solid State Physics, 1997
he iffet of the iletron±vongitudinl yptil honon sntertion on the hotoioniztion in untum ell ires ... more he iffet of the iletron±vongitudinl yptil honon sntertion on the hotoioniztion in untum ell ires eF liD wF pliyou I D nd rF voumrhri h eprtement de hysiqueD pult e des ienesD fFF RHIHD wekn esD woroo @eeived epril PQD IWWTY in revised form xovemer TD IWWTA he photon energy dependene of the photoioniztion rossEsetion is lulted for shllow donors in infinite potentil quntum well wires with retngulr rossEsetions s funtion of the size of the wireF he eletron±longitudinl optil @vyA phonon intertion is tken into ount using the strong oupling tretment for the impurity stte nd the veeEvowEines vritionl tretment for the sund finl stteF he results we otined show tht the photoioniztion rossEsetion nd the optil photoioniztion threshold energy re drmtilly dependent on the sizes of the wire nd re very sensitive to the eletron±vy phonon ouplingF IF sntrodution tudies of the strutures with quntum onfinement to one dimensionD iFeFD quntum well wires @sAD in whih the eletron motion long the length of the wire is tht of qusiEfree eletron nd is quntized in the two dimensions perpendiulr to the wireD re very interesting prolems in reent yersF he presene of ionized impurities in the s nd the smll sizes of these strutures ply fundmentl role in some physil properties suh s optil nd trnsport mehnism properties t low tempertureF his role eomes inresingly importnt s the dimensions of the wire rossEsetion eome smll nd it is thus quite different from tht in the ulk seF pew theoretil nd experimentl studies exist for optil properties suh s the photoioniztion rossEseE tion in the strutures with quntum onfinement to two dimensionsF kihw et lF I hve experimentlly nd theoretilly exmined the photoioniztion of deep trps in elqesGqes multiple quntum well lyers grown y metlorgni hemilEvpor depositionF ilEid nd omk PD Q hve lulted the dependene of the photoionizE tion rossEsetion on photon energy for shllow donors in quntum wells for light polrE ized long nd perpendiulr to the growth diretion with the ssumption of n infinite onfining potentilF wore reentlyD sliwi nd ilEid R improved their lultions y using finite potentil rrierF sn the qusiEoneEdimensionl struturesD there hs een some theoretil ttempts to study the optil properties in s S to IHF o our knowledgeD the photoioniztion rossEsetion hs not yet een performed in the qusiE oneEdimensionl semiondutorsF he present pper is devoted to the study of the spetrl dependene of the photoioniE ztion rossEsetion s" hw for polron ound to shllow hydrogeni impurity in inE I iFxFFD h eprtement de hysiqueD fFF fensoud SPHTD p esD worooF eF li et lFX iffet of iletron±vy honon sntertion on hotoioniztion IRS
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
Physica B-condensed Matter, 1997
The photon energy dependence of the photoionization cross-sections are calculated for a hydrogeni... more The photon energy dependence of the photoionization cross-sections are calculated for a hydrogenic shallow impurity located in quantum-well wires of GaAs, surrounded by Gal _.Al,As as a function of the sizes of the wire for several values of the heights of the potential barriers. The results we have obtained show that the photoionization cross-sections are affected by the sizes of the wire and the height of the barrier and also that their magnitude are larger than those in comparable infinite potential quantum-well wires.
Using the finite element method, the binding energies of a hydrogenic shallow donor impurity are ... more Using the finite element method, the binding energies of a hydrogenic shallow donor impurity are investigated in a cubic GaAs/ Ga 1Àx Al x A s quantum dot structure with realistic potential barrier height under the combined effect of hydrostatic pressure and temperature in the framework of the effective mass approximation. In the calculations, we have taken into account the electronic effective mass, dielectric constant, and conduction band offset between the dot and barriers varying with pressure and temperature. The results we have obtained show that the donor binding energy varies with the dot size, the confining potential, the position of impurity, the hydrostatic pressure and temperature. It is also found that the donor binding energy increases linearly with the pressure in direct gap regime and its variation is larger for narrower dots only and drops slightly with the temperature. A good agreement is obtained with the existing literature values.
c We examine the binding energy using the finite element method in quantum dots. c Large number o... more c We examine the binding energy using the finite element method in quantum dots. c Large number of finite elements and smaller mesh size h yield best results. c Our results of the binding energy agree with those of the variational method. c Increasing the potential barrier height will increase the impurity binding energy.