Effect of magnetic field on donor impurity-related photoionisation cross-section in multilayered quantum dot

The effect of the magnetic field on the electron states in the Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As multilayered quantum dot with and without shallow-donor impurity is under study. The magnetic field dependence of the impurity-related transition energies and the corresponding photoionisation cross-section is calculated, taking into account the excited states. The problem is solved using the effective mass approximation and rectangular potential profiles for wells and barriers using diagonalisation and finite element methods. The results obtained by both methods coincide with high accuracy. It is shown that the transition energies and photoionisation cross-section strongly depend on the impurity position and the magnetic field induction. As the magnetic field induction increases, all the peaks of photoionisation cross-section shift to the region of higher energies in the case of off-centre impurity and shift to lower energies in the case of on-centre impurity. The effect of merging two photoionisation cross-section peaks with increasing magnetic field induction is revealed, leading to a significant increase in the value of impurity photoionisation cross-section.