Heat Treatment Centers in Silicon

Heat treatment of p -type silicon at temperatures above 900°C frequently results in a decrease of hole concentration. In the present experiments, heat treatment centers have been found to diffuse from the surface during such heat treatments in the case of sufficient concentration to account for the observed changes in the electrical characteristics. The heat treatment center has a deep donor level at 0.4 eV above the valence hand. This level is converted into a donor level 0.51 eV from the conduction band at room temperature. Heat treatment centers may perhaps be introduced into silicon by surface impurity. Diffusion of the surface impurity is classified by its speed into two species. Faster diffusing one is characterized by the diffusion coefficient of 1×10 -5 cm 2 /sec at 1017°C and the activation energy for the solution, 1.8 eV. Observed properties on the heat treatment center show that heat treatment in the temperature range 900 to 1265°C results in diffusion of iron from the surface into bulk material.