Influence of exchange interaction on the energy spectrum and optical properties of resonant $D^-_2$-states in quantum wells of the external magnetic field

The interest to the impurity centers resonant states in quantum wells is associated with possibility to create new sources of stimulated emission at impurity transitions. The resonant $D^-_2$- states, which are formed as a result of connection of an electron by two neutral donors, are of particular interest. In this case, there are new possibilities for the control of the impurity molecular states terms, where the distance between the neutral donors and the spatial configuration of the $D^-_2$-center in the volume of the quantum well begin to play an important role. The aim of this work is to theoretically study the exchange interaction influence on the energy spectrum of the $D^-_2$-centers with the resonant g- and u-states in the quantum well in the presence of an external magnetic field, as well as on the impurity magneto-optical absorption in quantum multiwell structure with $D^-_2$-resonant states. The authors compare the obtained theoretical results with experimental data for dependence of the $D^-$-state binding energy on the external magnetic field in the quantum well GaAs / AlGaAs, doped with shallow donors of Si. To solve the problem of bound states for electron, which is localized on the $D^-_2$-center with the resonance g-and u-states in a parabolic quantum well in an external magnetic field, it is necessary to use the method of zero-range potential and the effective mass approximation. Calculation of the impurity magneto-optical absorption coefficient in the quantum multiwell structure with resonance $D^-_2$-states is conducted in the dipole approximation with account of the Lorentzian broadening for energy levels. The researcher investigate the dependence of the average binding energy of the resonant g-state for $D^-_2$-center on the external magnetic field with account of the Lorentzian broadening for energy levels. The scientists compare experimental data concerning the dependence of the electron binding energy for $D^-_2$-center on the external magnetic field in the GaAs / AlGaAs quantum well with shallow donors of Si and demonstrate a good agreement with theoretical calculations. It is supposed that the existence of resonant $D^-_2$-states, formed as a result of connection of electron by two neutral donors is possible under certain conditions in the GaAs / AlGaAs quantum wells, doped with shallow donors of Si. The exchange interaction between the $D^0$-centers can lead to the formation of resonant $D^-_2$-states in the quantum wells of GaAs / AlGaAs, doped with shallow donors of Si. The exchange interaction in the presence of oscillations of the interference nature, amplitude of which rapidly decreases with an increase of the average distance between neutral donors, is realized in the magneto-optical impurity absorption spectra in quantum multiwell structure.