Diffusion coefficients and activation energies were determined for Ge diffusion in strain-relaxed Si1-xGex, where x was 0, 0.1, 0.2, 0.3, 0.4 or 0.5. The activation energy decreased from 4.7eV for Si and Si0.90Ge0.10, to 3.2eV at an x-value of 0.5. This value was comparable with published data for Ge self-diffusion in Ge; thus suggesting that Ge-like diffusion occurred already at x-values of about 0.5. The effect of strain upon diffusion was also studied, and revealed a decrease in diffusion coefficient and an increase in activation energy upon going from compressive to tensile (table 2, figure 6).
Ge Self-Diffusion in Epitaxial Si1–xGex Layers. N.R.Zangenberg, J.Lundsgaard Hansen, J.Fage-Pedersen, A.Nylandsted Larsen: Physical Review Letters, 2001, 87[12], 125901 (4pp)
Table 2
Diffusivity of Ge in SiGe
Ge (%) | State | Temperature (C) | D0 (cm2/s) | E (eV) |
0 | relaxed | 925 – 1050 | 3.1 x 102 | 4.65 |
10 | relaxed | 925 – 1050 | 8.7 x 102 | 4.66 |
10 | compressive | 925 – 1050 | 6.7 x 101 | 4.33 |
10 | tensile | 925 – 1050 | 6.1 x 103 | 4.90 |
20 | relaxed | 900 – 1000 | 6.6 x 100 | 4.00 |
30 | relaxed | 875 – 975 | 4.7 x 100 | 3.82 |
40 | relaxed | 875 – 950 | 4.2 x 100 | 3.72 |
50 | relaxed | 850 – 950 | 1.1 x 10-1 | 3.23 |
Figure 6
Diffusivity of Ge in Si90Ge10
(Open circles: compressive; filled circles: relaxed; open squares: tensile)