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