Binding energies of ground and excited donor states bound to X valleys in GaAs/AlAs type-II quantum wells

We calculate the binding energies of $1s,$ $2s,$ ${2p}_x,$ ${2p}_y,$ and ${2p}_z$ donor states bound to X valleys in type-II GaAs-AlAs quantum well structures using an anisotropic variational method that enables us to take into account the effective-mass anisotropy and the quantum confinement. These binding energies present a strong dependence on the effective mass and the valley symmetry. Intradonor $1\overrightarrow{s}2p$ transitions energies are shown to be up to 1000 ${\mathrm{cm}}^{-1},$ which is well above the energies usually observed for donors in type-I quantum structures.