Remote and spatially separatedD−centers in quasi-two-dimensional semiconductor structures

The electronic structure, binding energy, and correlation functions of three different spatial configurations of ${\mathrm{D}}^{\mathrm{-}}$ centers in GaAs-based semiconductor structures are studied using a numerical technique that solves the two-electron Schrödinger equation for such systems. We compare our results for the quantum well ${\mathrm{D}}_{\mathrm{w}}^{\mathrm{-}}$ with experimental data and variational and diffusion Monte Carlo calculations. We demonstrate the existence of the spatially separated ${\mathrm{D}}_{\mathrm{s}}^{\mathrm{-}}$ center as a bound state, even in the regime of very low magnetic fields, and find interesting anticrossings among the energy levels in its electronic structure, which underlie a spectrum composition of a ${\mathrm{D}}^0$ donor center and a free electron in a magnetic field. For the remote ${\mathrm{D}}_{\mathrm{r}}^{\mathrm{-}}$ center we find that strong electron-electron correlations can give rise to magnetic-field-induced angular-momentum transitions, and as the magnetic field increases, these correlations weaken, while eventually the system magnetically evaporates approaching the classical unbound regime.