Anodization etching and radioactive tracer analyses were used to study the self-diffusion of 31Si in single crystals having various degrees of perfection and doping. The oxygen content of the Si was about 5 x 1017/cm3 and the dislocation densities were of the order of 102/cm2 or less. For intrinsic material at between 1100 and 1300C:

D(cm2/s) = 9 x 103exp[-5.13(eV)/kT]

Doping to above intrinsic levels increased the diffusion coefficient (table 106). It was proposed that Si diffused via a vacancy mechanism. The influence of n-type doping was attributed to the increase in total vacancy concentration caused by the excess electrons.

Self-Diffusion in Intrinsic and Extrinsic Silicon. J.M.Fairfield, B.J.Masters: Journal of Applied Physics, 1967, 38[8], 3148-54

Table 106

Diffusion of 31Si into Extrinsic Si

Dopant | Concentration (/cm3) | Temperature (C) | D (cm2/s) |

As | 7.0 x 1019 | 1183 | 2.10 x 10-14 |

P | 1.88 x 1020 | 1197 | 4.70 x 10-14 |

B | 8.0 x 1019 | 1197 | 2.32 x 10-14 |

As | 1.3 x 1020 | 1088 | 2.31 x 10-15 |

As | 1.8 x 1020 | 1088 | 2.53 x 10-15 |

P | 9.0 x 1019 | 1086 | 2.30 x 10-15 |

P | 8.0 x 1019 | 1093 | 1.83 x 10-15 |

P | 1.88 x 1020 | 1096 | 3.90 x 10-15 |

B | 8.0 x 1019 | 1092 | 1.20 x 10-15 |

B | 2.2 x 1020 | 1090 | 1.75 x 10-15 |

As+B | 1.4 x 1020 each | 1187 | 1.55 x 10-15 |