Diffusion doping of silicon with magnesium

Doping of silicon with magnesiumis 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°C, 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 x 10^14 and 5 x 10^14 cm ^-3, 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.