Effect of Hermanson's spatial dielectric function on donor impurity binding energy in a cylindrical cross-sectional GaAs/GaAlAs quantum well wires on infinite length

512-514We have used a variational technique to calculate the binding energy of a hydrogenic donor impurity in the dielectric regime and that of non-hydrogenic donor impurity in the Hermanson's spatial dielectric function regime. The results show, in both cases, the usual increase in binding energy with decreasing quantum well wire (QWW) radius obtained by Csavinszky and Oyoko [Phys Rev B,43 (1991) 9262]. However, in this work we have also calculated the va riation with QWW dimensions. The results show that the difference in donor binding energy in the two regimes under consideration varies with QWW radius: As the QWW decreases the binding energy difference increases slowly up to a QWW radius of abou t 60 atomic units (aa) Then for smaller radius it increases more rapidly with decreasing QWW radius

Theoretical Study of effect of spatial dielectric function on binding Energy of Donor impurity located on varying pusitions along Z-axis of GaAs quantum well dot of circular cross-section

467-470<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">A theoretical study has been carried out of a donor impurity binding energy in a GaAs/Ga1-x AlxAs Quantum Well Dot (QWD) of circular cross-section and finite length. The derivation of the binding energy was carried out for a potential screened by a dielectric constant, εo, and a spatial dielectric function ε(ρ, z) that varies as the radius and length of the QWD. The donor impurity was placed on varying positions, zi, along the axis of the QWD. A general feature of the results is that in both the dielectric constant and spatial dielectric function regimes, the binding energies were the same at large values of the QWD radius, R, and length, L. However, for smaller radii and length the binding energy in both cases showed marked increase with decreasing QWD radii and length with the binding energy showing a faster increase in the spatial dielectric function regime than in the dielectric constant regime. This feature is seen when the radius is decreased while the length is kept constant and when the length is decreased and the radius is kept constant. The same feature is also seen when the radii and the length are kept constant while the position of the impurity is decreasing towards the origin. These features suggest that in determining the binding energy of a donor impurity in such geometries consideration should be taken of the effect of spatially varying dielectric function.</span

Theoretical study of the effect of applied stress on the binding energy of a donor impurity in GaAs quantum well dot within an infinite potential barrier

908-911A theoretical study has been carried out on the effect of applied stress on the binding energy of a shallow monovalent donor impurity in a GaAs quantum well dot (QWD) of square cross-section. In our calculations, a variational technique [Csavinzky &amp; Oyoko, Phys Rev B, 43 (1991) 9262.] within the effective mass approximation has been used. In our model the donor impurity is confined to the QWD by an infinite barrier potential unlike in a previous study [Oyoko et al. J Appl Phys, 90 (2001) 819.] where the barrier potential was finite. The donor impurity was located at various positions along the axis (Z-direction) of the QWD. The stress was applied along the same axis. The results show that for constant QWD dimensions Lx, Ly and Lz, for various donor positions, the binding energy increases with the applied stress as the donor position varies from on-edge to on-center locations. The binding energy is also found to increase as the QWD length decreases in both cases of on-edge and on-center donor locations for constant Lx and Ly as well as for decreasing QWD size. In all the cases considered, the binding energy is much larger for the on-center than for the on-edge positions for the same QWD dimensions and the same applied axial stress. The results obtained show that in experimental study of optical and electronic properties of such nanostructures as QWDs, the effect of stress on donor impurity binding energies should be taken into consideration