Calculations of the binding energy of the outer electron in the ground state of $D^{-}$ centers in Si as a function of uniaxial stress along the [100] direction show that, for centers associated with group V substitutional donors, the binding is not a monotonic function of stress. As the stress increases from zero, the outer electron becomes localized in the two stress-deepened valleys, which leads to a decrease in binding energy. With further increase in stress the inner electron is gradually forced into the same two valleys, increasing the binding energy. Calculated results for Si:P are compared to experiment. The stress dependence of the binding energy of $D^{-}$ in Si:Li, which is quite different, is also discussed.

• Received 17 November 1980

DOI:https://doi.org/10.1103/PhysRevB.23.5521