Diffusion of Magnesium in Czochralski Silicon

The diffusion of magnesium in monocrystalline dislocation‐free Czochralski silicon (Cz–Si) with an oxygen concentration of (3–4) × 1017 cm−3 is studied. Initial silicon wafers are doped with Mg by using the sandwich technique. The impurity diffusion profiles are investigated in n‐Si samples by the differential conductivity method. The diffusivity of electrically active magnesium in the temperature range of 1,100–1,250 °C is two to three orders of magnitude lower than the values observed at doping high‐purity silicon crystals grown by the float‐zone method (Fz–Si). The diffusion in Cz–Si is retarded through the trapping of diffusing Mg atoms by oxygen‐related traps. The observed high value of the activation energy of Mg diffusion in investigated samples (4.1 eV) is due—along with the migration energy of interstitial magnesium in the crystal lattice (1.83 eV) —to the significant binding energy of Mg atoms with traps (2.27 eV). A study of the temperature dependence of the Hall effect in bulk‐doped samples reveals two types of deep double donors: interstitial Mg atoms and MgO complexes. Complexes of magnesium with oxygen in silicon are of interest given possible applications in infrared silicon photonics. Diffusion doping of Czochralski‐grown silicon with magnesium reveals a dramatic decrease of Mg diffusivity compared to the high‐purity crystals obtained by the float‐zone method. The finding is discussed within a model of the trap‐limited diffusion of Mg atoms in Czochralski silicon.