Correlation Factor for the Diffusion of Charged Impurities in the Diamond Structure*

The correlation factor for impurity diffusion by a vacancy-mechanism is a function of the vacancy-jump frequencies in the surroundings of the diffusing atom. Since in Si and Ge the vacancy can act as an acceptor, a long-range Coulomb interaction between donor atoms and vacancies exists. The usual assumption, that only a few vacancy-jump frequencies in the im­ mediate surroundings of the vacancy are different from the jump frequency in the pure matrix, is not justified in this case. A very general expression for the correlation factor of impurity-diffusion in the diamond structure is deduced. Vacancy-jump frequencies for jumps which originate from first-, second-, and third-nearest neighbours are treated explicitely. For more remote jumps the Coulomb force is taken into account as a drift force operating on the migrating vacancy. After specializing the general expression it is compared with the well-known ,,four-frequency-model” of Manning.