Generation of thermal donors as a result of one- and two-step annealing of silicon crystals with large and small carbon concentrations

In studies of the effect of carbon on the formation of thermal donors during one- and two-step annealings in oxygenated silicon crystals in the temperature interval 400-800 degrees C, it is shown that the presence of a carbon impurity in large concentrations, comparable with the oxygen impurity content in them (similar to 8 x 10(17) cm(-3)), results mainly in the formation of singly charged shallow thermal donors with thermal ionization energies in the range 24-38 meV and g factors in the interval 1.9985-1.9993, of which a significant fraction is thermally stable against annealings at higher temperatures. Subcritical oxygen clusters generated at carbon atoms appear in the role of the latter. Neither ordinary doubly charged thermal donors nor thermal accepters such as Si-NK centers are formed in such crystals. (C) 1996 American Institute of Physics.