Doping of silicon with magnesium is investigated by a sandwich diffusion technique. Temperature dependence of the diffusion coefficient in the dislocation-free silicon in the range of 1000-1200 8C is determined. It obeys the Arrhenius behavior over the range of 600-1200 8C, when the data obtained earlier for the lower temperatures are taken into consideration. Preliminary results on Mg diffusion in the dislocated crystals are also presented. The dislocation-free Si:Mg samples are investigated with the Hall-effect measurements and the low-temperature Fourier spectroscopy. A decrease in concentration of Mg interstitials (about 15%) has been observed after 31 months of the samples storage at room temperature, when a commercially available FZ silicon was used as a starting material. The effect of the samples degradation is proposed to be due to a formation of Mg-O complexes. When using a special silicon purified from oxygen and carbon with concentrations below or equal to 1.5 Â 10 14 and 5 Â 10 14 cm À3 , respectively, a decrease in the density of interstitial magnesium has not been noticed during this period. The storage of Si:Mg samples prepared from pure silicon gives rise to the formation of an unknown center, whose ionization energy is between the corresponding values for the interstitial Mg 0 centers and (Mg-O) 0 complexes.

The deep double donor levels of substitutional chalcogen impurities in silicon have unique optical properties which may enable a spin/photonic quantum technology. The interstitial magnesium impurity (Mgi) in silicon is also a deep double donor but has not yet been studied in the same detail as have the chalcogens. In this study we look at the neutral and singly ionized Mgi absorption spectra in natural silicon and isotopically enriched 28-silicon in more detail. The 1s(A1) to 1s(T2) transitions, which are very strong for the chalcogens and are central to the proposed spin/photonic quantum technology, could not be detected. We observe the presence of another double donor (Mgi * ) that may result from Mgi in a reduced symmetry configuration, most likely due to complexing with another impurity. The neutral species of Mgi * reveal unusual low lying ground state levels detected through temperature dependence studies. We also observe a shallow donor which we identify as a magnesium-boron pair.arXiv:1806.01965v3 [cond-mat.mtrl-sci]

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The Lyman absorption spectra of different shallow dopants in elemental semiconductors at liquid-helium temperature show typically transitions from the even-parity ground state to odd-parity excited states. Such transitions are dipole allowed and observed by absorption spectroscopy. Knowledge on the excited states with other type of symmetry can be derived from absorption and Raman spectra of a heavily doped semiconductor, or at experimental conditions enabling optical dipole-allowed transitions from or into even-parity states. Here, we report on the experimental observation of impurity transitions involving different excited even-parity (ns-and nd-) states in silicon crystals: 1) doped with group-V hydrogen-like donors in samples with large infrared absorbance, and 2) doped with the magnesium double donor evoking a thermal population of the lowest even-parity excited states.

The high-temperature gas-phase doping of silicon with sulfur has been studied at various sulfur vapor pressures. It is shown that the content of one-and two-atom sulfur-related deep donors in the semiconductor can be quantitatively controlled by varying the diffusant vapor pressure.