Examining the influence of magnetic field on a donor dopant’s photoionization cross-section in a double quantum box

Abstract

This study systematically explored the binding energy and the photoionization cross-section (PCS) of a hydrogenic shallow donor impurity within a GaAs double quantum box structure incorporated into a Ga(1−x)Alx As matrix under the influence of an external intense magnetic field. The computations are performed using the effective-mass approximation (EMA) and the finite element method (FEM), taking into account a finite potential across all surfaces of the nanosystem. The results emphasize the significant role of the magnetic field, primarily in enhancing the donor binding energy within the double quantum box system. We demonstrate that increasing the magnetic field results in an augmentation of binding energy across various aluminum concentrations. The PCS of a shallow donor impurity undergoes a blue shift when shifted from the barrier center to the box center, attributed to the increased binding energy. When the double quantum box is subjected to a magnetic field effect, the amplitude peaks of PCS show an elevation coupled with a blue shift. By setting magnetic field values at 0 T, 35 T, or 70 T and varying aluminum concentrations, we observe a shift in the PCS towards higher energy levels along with an increase in peak amplitude. We also study the PCS of the donor impurity as a function of photon energy, mainly examining the effects of box width and barrier width modifications in the double quantum box.