The co-evaporation of B2O3 during Si molecular beam epitaxial growth at temperatures of between 540 and 800C was used to prepare superlattice structures with B concentrations which ranged from 3 x 1018 to 3 x 1020/cm3. The superlattices were then annealed and studied by using secondary ion mass spectrometry, electrochemical profiling and cross-sectional transmission electron microscopy. It was found that an appreciable redistribution of B, at high B concentrations, occurred before annealing when the growth temperature was greater than 700C. The diffusivity of B in the layers was found to depend markedly upon the growth temperature (table 143).
T.E.Jackman, D.C.Houghton, J.A.Jackman, M.W.Denhoff, S.Kechang, J.McCaffrey, A.Rockett: Journal of Applied Physics, 1989, 66[5], 1984-92
Table 142
Ambient Diffusion of B as a Function of B Dose, Ge Dose, and Incompatibility Stress
B (/cm2) | Ge (/cm2) | S (N/m2) | D (cm2/s) |
6 x 1014 | 0 | 4 x 107 | 2.5 x 10-13 |
6 x 1014 | 5 x 1015 | - | 8 x 10-14 |
6 x 1014 | 1 x 1016 | - | 5 x 10-14 |
1.3 x 1015 | 0 | 9 x 107 | 4 x 10-13 |
1.3 x 1015 | 5 x 1015 | 6 x 107 | 2.5 x 10-13 |
1.3 x 1015 | 1 x 1016 | 5 x 107 | 1.3 x 10-13 |
2 x 1015 | 0 | 1.5 x 108 | 5 x 10-13 |
2 x 1015 | 5 x 1015 | - | 4 x 10-13 |
2 x 1015 | 1 x 1016 | 1 x 107 | 2.5 x 10-13 |