On Binding Energy of Trions in Bulk Materials.

We study the negatively $T^{-}$ and positively $T^{+}$ charged trions in bulk materials in the effective mass approximation within the framework of a potential model. The binding energies of trions in various semiconductors are calculated by employing Faddeev equation in configuration space. Results of calculations of the binding energies for $T^{-}$ are consistent with previous computational studies and are in reasonable agreement with experimental measurements, while the $T^{+}$ is unbound for all considered cases. The mechanism of formation of the binding energy of trions is analysed by comparing contributions of a mass-polarization term related to kinetic energy operators and a term related to the Coulomb repulsion of identical particles.