Metastable One- and Two-Electron donor States in GaAs and CdF$\text{}_{2}$

The strongly localized one-electron (D$\text{}^{0}$) and two-electron (D¯) donor states are considered with the lattice deformation around the donor center taken into account. For GaAs, the donor energy levels have been calculated as functions of the hydrostatic pressure. The calculated energy positions and pressure coefficients agree with the experimental data. It is shown that the interaction with phonons reduces the probability of radiative transitions between the states of different localization and leads to the metastability of shallow-level donor states with respect to the D¯ state in GaAs and both the states (D$\text{}^{0}$ and D¯) in CdF$\text{}_{2}$.