Effect of Doping with Shallow Donors on Radiative and Nonradiative Relaxation in Silicon Nanocrystals: Ab Initio Study

Electronic structures of 1-2 nm in diameter hydrogen-passivated silicon nanocrystals and rates of the radiative interband transitions and Auger recombination were calculated on the basis of first-principles (DFT/TDDFT) methods for the nanocrystals doped with a single centrally located phosphorus or lithium atom. We have found a significant increase of the radiative recombination rates caused by the nanocrystals' doping at room temperature. For the P-doped crystallites, this effect takes place at zero temperature as well, while the Li-doped crystallites (at least, some of them) demonstrate strong temperature dependence of the recombination rates, which drastically drop as the temperature decreases. The rates of the Auger recombination in the nanocrystals with Li, on the whole, turn out to be of the same order of magnitude as in the undoped nanocrystals. On the contrary, in the P-doped nanocrystals, the Auger process becomes considerably slower.