Thermal donors were generated in Czochralski-grown samples by heat-treatment at about 450C. They formed several individual effective mass-like donors having slightly different ionization energies, and acted as double donors. Heat-treatment above 500C led to competition between the formation and annihilation of thermal donors. A study was made of the formation and annihilation of thermal donors at temperatures ranging from 520 to 700C. Czochralski-type samples with an initial total thermal donor concentration of about 5 x 1015/cm3 were used to study the annihilation of thermal donors. The number of interstitial O atoms which was generated per annihilated thermal donor center depended upon the temperature, and ranged from 4 to 24. Within the temperature range which was investigated, the activation energy for the thermal annihilation of thermal donors was deduced to be 2.5eV. The same material, but with an initial thermal donor concentration of about 2 x 1013/cm3, was used to study the formation of thermal donors. During annealing, the concentrations of individual thermal donors attained equilibrium concentrations which depended upon the temperature of the final annealing step and the total O concentration. It was demonstrated that a model in which the individual centers were represented by O clusters of various sizes consistently explained the experimental data.

Thermal donor formation and annihilation at temperatures above 500C in Czochralski-grown Si W.Götz, G.Pensl, W.Zulehner, R.C.Newman, S.A.McQuaid: Journal of Applied Physics, 1998, 84[7], 3561-8