Theory of excitons bound to neutral impurities in polar semiconductors

The ground-state energy and the configuration of a complex consisting of an exciton bound to a neutral impurity are investigated. Starting from a Hamiltonian which includes the electron-phonon coupling as described by Fr\"ohlich, we derive a mass renormalization and an effective electron-hole potential, both depending on the interparticle distances. The corresponding Schr\"odinger equation is solved by an ansatz which describes an exciton bound to a donor as well as to an acceptor. In addition, central-cell effects are taken into account. Numerical results for several III-V and II-VI compounds are in good agreement with experimental data.