Binding Energy Of Shallow Impurities Research Articles

Shallow impurity binding energy in lateral parabolic confinement under an external magnetic field

We have described the calculation of hydrogenic impurity binding energies in cylindrical GaAs–Ga 1− x Al x As quantum well wires (QWWs) with lateral parabolic confinement in the presence of an axial magnetic field. The numerical calculations of this system have been performed with the use of a variational procedure in the effective mass approximation. We observed sharp changes in binding energy for critical spatial confinement radius and B magnetic field values.

Hydrogenic impurity states in semiconducting nanostructures with anisotropic effective mass

A hydrogenic impurity located in a semiconducting nanostructure with anisotropic effective mass of carriers m * = { m ⊥ , m ⊥ , m ∥ } is investigated with variation of the impurity position taken into account. A binding energy and deformation of the impurity are analyzed as a function of the layer thickness and impurity position in 2D structures with different effective mass of carriers. The results obtained for the shallow impurity binding energy are in a good agreement with the theoretical calculations both for bulk semiconductors [W. Kohn, J.H. Luttinger, Phys. Rev. 98 (1955) 915] and 2D semiconductors with isotropic effective mass of electrons [G. Bastard, Phys. Rev. B 24 (1981) 4714].

Binding energy of shallow impurities in a polar quantum well wire

The binding energy of an on-center donor impurity in cylindrical quantum well wire is investigated. The calculation is made within the effective mass approximation and using a variational approach. The electronic confinement was modeled by a finite deep potential well. The interaction of the charge carriers (electron and ion) with both the confined LO and SO phonons has been considered. Our results show that the binding energy and the electron effective mass depend on the size of the wire, the height of the potential barrier and the polaronic corrections. Furthermore, for a thin wire the binding energy depends also on the variation of the electron effective mass at the edge of the wire.

Effects of an applied electric field on the binding energy of shallow donor impurities in GaAs low-dimensional systems

Using a variational procedure within the effective-mass approximation we calculate the binding energy of a shallow donor impurity in cylindrical GaAs low-dimensional systems, under the action of an electric field applied in the axial direction, and considering an infinite confinement potential. We calculate the dependence of the binding energy on the system geometry, the applied electric field, and the donor-impurity position. Our results for small fields and large radius as well as for length greater than the radius coincide quite well with previous results in quantum wells, quantum-well wires, and quantum dots. We find that a proper knowledge of the impurity distribution inside the GaAs low-dimensional system is of relevance in a qualitative comparison between theoretical and experimental results concerning the binding energy of shallow impurities under the action of an applied electric field.

Effect of spatially dependent screening on the binding energy of shallow impurities in spherical GaAs-(Ga,Al)As quantum dots

Within the effective-mass approximation and using a variational method the binding energies of hydrogenic impurities in spherical GaAs-(Ga,Al)As quantum dots are calculated considering the effect of a spatially dependent screening through an r-dependent dielectric response. It is found that the r-dependent dielectric response increases the binding energies when compared with those found using constant screening. The effect is more important for acceptors than for donors and must be taken into account in calculations that include the binding energies of acceptors impurities in GaAs-(Ga,Al)As quantum dots.

Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

ABSTRACTThe reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.

Analytical results for semiconductor quantum-well wire: Plasmons, shallow impurity states, and mobility.

We present a theoretical investigation of the electronic properties of a quasi-one-dimensional electron system at very low temperature. For a cylindrical quantum wire the electron-impurity interaction and the electron-electron interaction is calculated for a two-subband model. Our analytical results for the electron-impurity and the electron-electron interaction are in good agreement with the exact results for our model. Analytical results for the band bending due to the filling of the lowest subband are evaluated. Within our analytical results we discuss various aspects of the electronic properties of the semiconductor quantum wire: screening (intrasubband and intersubband plasmons), shallow impurity states (screened and unscreened), and mobility (ionized-impurity scattering and interface-roughness scattering). Analytical expressions are given for the dispersion of plasmons, the binding energies of shallow impurities, and the mobility. Our results on intersubband plasmons are compared with experiments.