Effects of electric and magnetic fields on confined donor states in a coupled double quantum well
ABSTRACT We have developed a variational formalism to calculate the effects of electric and magnetic fields on confined hydrogenic donor states in asymmetric coupled double quantum well structures. It is demonstrated that an electric field applied along the growth axis can easily shift the electron wave function from one quantum well across the center barrier into the neighboring well, without ejecting the electron from a confined donor state. Depending on donor location in the structure, binding energy can either increase or decrease under the applied electric field, as had been found in the case of single quantum wells, but with significantly greater rates of change in response to the external field. The magnetic field applied along the growth axis of the quantum well structure leads to additional quantum confinement, increasing both the donor binding energies and the transition energy between the 1s and 2p + donor states. Effect of the relative size of the two coupled quantum wells on the donor binding energy is also discussed. Dipole moment and polarizability of the confined donor states are obtained simultaneously as well.
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ABSTRACT: The binding energy of the donor impurity in double triangle quantum well (DTQW), double graded (DGQW) and double square (DSQW) GaAs–(Ga,Al)As quantum wells under the electric field is calculated by using a variational approach. The results have been obtained in the presence electric field applied along the growth direction as a function of the impurity position, barrier width and the geometric shape of the double quantum wells. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)physica status solidi (b) 03/2004; 241(5):1066 - 1072. · 1.49 Impact Factor
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ABSTRACT: Using a variational method and within the effective mass approximation, we calculate the laser-field dependence of binding energy and the polarizability of shallow-donor impurities in graded quantum wells under an external static electric field. We have shown that, in the graded quantum well structures, not only the 'dressed' potential but also the direction of the external electric field parallel to the growth direction play very important roles in the determination of the binding energy and the polarizability of a hydrogenic impurity.Semiconductor Science and Technology 04/2003; 18(6):470. · 1.92 Impact Factor
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ABSTRACT: We analyze the effect of the mixing of the low-lying s and px ,y subbands on the ground-state binding energy of the off-axis donors in cylindrical nanotubes in the presence of a magnetic field parallel to the axis. We express the wave function as a product of combinations of s and p subband wave functions and an envelope function that depends only on the electron–ion separation. By using the variational principle we derive a differential equation for the envelope function, which we solve numerically. The curves for the dependence of the ground-state binding energies on the donor distance from the axis are presented and it is shown that the effect of the subband mixing for off-axis donors in nanotubes is considerable. It is found that the magnetic field enhances the binding energies of donors located close to the axis whereas for donors located far from the axis the effect of the magnetic field on the binding energy is the opposite. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)physica status solidi (b) 03/2006; 243(6):1263 - 1268. · 1.49 Impact Factor