Germanium self-diffusion

The technology of silicon and germanium production has developed rapidly, and knowledge of die self-diffusion properties of diese elements, and of impurity atoms has become reasonably accurate despite die experimental difficulties associated widi die measurements. These arise from die chemical affinity of diese elements for oxygen, and from die low values of die diffusion coefficients. 

It will be noted that because of the low self-diffusion coefficients the numerical values for representations of self-diffusion in silicon and germanium by Anhenius expressions are subject to considerable uncertainty. It does appear, however, that if this representation is used to average most of the experimental data the equations are for silicon... 

W. Frank. The interplay of solute and self-diffusion—A key for revealing diffusion mechanisms in silicon and germanium. In D. Gupta, H. Jain, and R.W. Siegel, editors, Defect and Diffusion Forum, volume 75, pages 121-148, Brookfield, VT, 1991. Sci-Tech Publications. 

A short compilation of important diffusion coefficients is presented in Table 3.7. Several features are of note here. The first is the strong dependence on temperature that we see in the diffusivities of boron in germanium, and the self-diffusion of Si. A 10 to 20% increase in absolute temperature can lead to a rise in diffusivity of several orders of magnitude. The temperature dependence is clearly an exponential one and is commonly expressed by an Arrhenius-type relation ... 

The diffusion of dopants in semiconductors has been briefly discussed in Sect. 2.1.3. At an atomic scale, the diffusion of a FA in a crystal lattice can take place by different mechanisms, the most common being the vacancy and interstitial mechanisms in silicon and germanium (see for instance [25]). The interstitial/substitutional or kick-out mechanism, which is an interstitial mechanism combined with the ejection of a lattice atom (self-interstitial) and its replacement by the dopant atom is also encountered for some atoms like Pt in silicon. 

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