Ground states of the D− ion in multivalley semiconductors were investigated using a diffusion quantum Monte Carlo method, under the condition that the central-cell correction for a donor ion could be neglected. The D− binding energy, EBD-, was estimated for the intravalley configuration with the use of a donor binding energy, EBDo, as EBD- being approximately equal to 0.055EBDo, if the anisotropy of the effective mass was not so large. The anisotropy of the effective mass being large, the D− binding energy increased greater than 0.055EBDo. This was due to the enhancement of the correlation effect between two electrons in a D− ion with lowering dimension. For the intervalley configuration, the D− binding energy was further increased because the repulsive Coulomb energy between trapped electrons could be effectively suppressed. The calculated results reproduce well the experimental ones for Si and Ge, in which the intravalley or the intervalley configuration was well controlled.

Negative Donors in Multivalley Semiconductors - Diffusion Quantum Monte Carlo Simulations. J.Inoue, J.Nakamura, A.Natori: Physical Review B, 2008, 77[12], 125213 (5pp)