Stress effects on shallow-donor impurity states in symmetricalGaAs/Alx<

Abstract

The effects of the compressive stress on the binding energy and the density of shallow-donor impurity states in symmetrical GaAs/Al x Ga 1Ϫx As double quantum wells are calculated using a variational procedure within the effective-mass approximation. Results are for different well and barrier widths, shallow-donor impurity position, and compressive stress along the growth direction of the structure. We have found that independently of the well and barrier widths, for stress values up to 13.5 kbar ͑in the direct-gap regime͒ the binding energy increases linearly with the stress. For stress values greater than 13.5 kbar ͑indirect gap regime͒ and for impurities at the center of the wells, the binding energy increases up to a maximum and then decreases. For all impurity positions the binding energy shows a nonlinear behavior in the indirect gap regime due to the ⌫-X crossing effect. The density of impurity states is calculated for a homogeneous distribution of donor impurities within the barriers and the wells of the low-dimensional heterostructures. We have found that there are three special structures in the density of impurity states: one associated with on-center-barrier-, the second one associated with on-center-well-, and the third one corresponding to on-external-edge-well-impurity positions. The three structures in the density of impurity states must be observed in valence-to-donor-related absorption and conduction-to-donor-related photoluminescence spectra, and consequently these peaks can be tuned at specific energies and convert the system in a stress detector.

Infinite potential barrier and hydrostatic pressure effects on impurity-related optical absorption spectra in GaAs double quantum wells

“…It is important to point out that the 30 kbar value is beyond the Γ − X transition, which starts at 13.5 kbar, so the barrier height is smaller close to 40 meV and the binding energy is larger as discussed in references [6,7]. This is in agreement with the energy-pressure relation reported in [6,7]. Fig.…”

“…The infinite barrier boundary conditions may contribute as well to this the effect, as can be seen from fig. 5 in reference [7]. There, the curve looks like the other two curves.…”

“…In order to include the pressure dependent Γ − X mixing, we have followed the phenomenological model suggested by Elabsy [5]. The trial wave function for the ground state is chosen as [6,7] …”

“…In the last years, the study of hydrostatic pressure on the optical properties of quantum confined structures have been widely investigated [1][2][3][4][5][6][7]. Even since the advent of layered semiconductor structures, one of the main research interests has been the study of the optical properties of semiconductor quantum wells (QW).…”

“…The effects of the Γ − X crossover pressure at low-temperatures on the donor binding energies in QW heterostructures have been studied by Elabsy [5]. The combined effect of hydrostatic pressure and applied electric field on the binding energy and density of shallow impurity states (DOIS) in symmetrical and asymmetrical GaAs-Ga 1−x Al x As double quantum wells (DQW) have also been calculated [6,7].…”