Exchange-coupled dopants in Si quantum dots

The electronic structure of exchange-coupled donors in Si quantum dots (QDs) is predicted using effective mass theory, enabling the calculation of many dopant configurations. We account for the statistical distribution of dopants in QD ensembles with a broad range of mean sizes and doping concentrations. A quenching of the magnetic resonance intensity of exchange-coupled donors is inferred, which is more pronounced for smaller QDs. We further show that in QDs smaller than similar to 2.5 nm, the quantization (and broadness) of the distribution of exchange energies yields a step-like behavior in the magnetic resonance temperature dependence, as observed in recent experiments. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748324]