Electronic structure of donor-impurity complexes in quantum wells

Abstract

The ground state of the two-electron donor-impurity complexes and confined in a quantum well is analysed by using a variational procedure. A model approximation that can be used in the two-electron problem in order to separate the variables is proposed, and it is shown that, for the negative ion and the complex, the electron-electron interaction may be eliminated, in this approximation, by introducing an additional effective charge at a centre of symmetry. The binding energy is calculated as a function of the quantum-well width for different magnetic field strength values, whereas the and dissociation energies are calculated as functions of the spacing between the impurities in the complexes, and for different well widths. The results for the first and the second ionization binding energies as functions of the well width are presented for different separations between impurities. Finally, the scheme that we propose is extremely simple and provides a realistic description of few-particle ground-state electronic structures confined in a quantum well.

Off-Center Neutral and Negatively Charged Donor Impurities in Semiconductor Heterostructures: Fractal Dimension Method

“…The maximum value of the D --binding energy in QWW in Fig. 10 is approximately 1.23 Ry* which corresponds to an intermediate value between 0.326 Ry * and 2.41 Ry * obtained previously for QW [19] and QD [21]. The curve for the zero magnetic field in Fig.…”

“…The confinement effect imposed by the quantum well on both the D --and D 0 binding energies in different semiconductor heterostructures has been analyzed in a considerable number of theoretical investigations [11][12][13][14][15][16][17][18][19][20][21]. The diffusion quantum Monte Carlo [11,12] and variational [13][14][15][16][17][18][19][20][21] methods have been used to calculate the D --groundstate binding energy in quantum wells (QWs) and quantum dots (QDs).…”

“…The diffusion quantum Monte Carlo [11,12] and variational [13][14][15][16][17][18][19][20][21] methods have been used to calculate the D --groundstate binding energy in quantum wells (QWs) and quantum dots (QDs). A great part of these works analyze the on-center D --problem in QWs and multiple QWs by using a Chandrasekhar-type trial function with various nonlinear variational parameters (up to 9).…”

Stability of D – in quantum wells under strong magnetic fields

“…In the past years, quasi-two dimensional semiconductor quantum wells (QWs) have been studied extensively both theoretically and experimentally, and it has been established that the binding energy of neutral (D 0 ) and negatively charged (D − ) donors in these systems is increased due to the unilateral confinement in the direction of crystal growth [1][2][3][4][5][6][7][8][9]. Besides, an external magnetic field applied in the same direction produces an additional increase of the binding energy by contracting the electron density distribution in the plane perpendicular to the growth axis [2][3][4][5][6][7][8][9]. Until now, the previous theoretical calculations of the ground state binding energy for off-center D − in QWs have been carried out for models in which is assumed that the coupling between the motion in the z direction and the x-y plane can be neglected because of the strong confinement along the z axis [10].…”

Negative-Donor in Graded Quantum Well-Wire: Fractal Dimension Approach

“…Initially found in bulk only under metastable conditions [4], a negative-donor is analogous to the H À ion, which offers an interesting example of a few-particle system where the electron-electron correlation plays a decisive role in trapping and keeping of a second electron [5,6]. The diffusion quantum Monte Carlo [7] and variational [8][9][10][11][12][13][14] methods have been used to calculate the D À ground state binding energy in semiconductor heterostructures. An increasing of the D À binding energy up to 10 times in QWs and up to 50 times in quantum dots (QDs) produced by the confinement has been found.…”