Site dependence of donor properties in ZnSe and validity of effective-mass theory

An analysis of luminescence data has given the binding energy and radius of the Li interstitial donor in ZnSe, as well as the transition probability, relative to that of the ${\mathrm{Al}}_{\mathrm{Zn}}$ substitutional donor, for donor-acceptor pair luminescence. The radius of the ${\mathrm{Al}}_{\mathrm{Zn}}$ donor has also been obtained. These results, combined with appropriate prior data on ZnSe donors, show that there is a striking site dependence of donor properties, particularly for the transition probability (by orders of magnitude). Moreover, it is pointed out that the results cannot be understood within effective-mass theory, despite the fact that the values of the energies and radii imply that this theory should apply; this poses a fundamental theoretical puzzle.