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Sunday, January 12, 2014

#272 Problems with doping

Ability to control conductivity of semiconductors in general, and conductivity type (n- or p-type) specifically, is a cornerstone of any semiconductor device fabrication. As we all know, it is accomplished by introduction of the minute amounts of alien elements, known as dopants, into semiconductor structure. It can be done either homogenously during material growth or selectively by implantation or diffusion into the substrate wafer during device manufacturing.


Easy, right? Well, not necessarily. Ease with which silicon and germanium can be doped is misleading in the sense that these two are the only semiconductors, elemental or compound, in which doping is a straightforward matter. Among reasons for which other semiconductors do not readily lend themselves to selective doping the most important include: lack of elements which would act as either n- or p-type dopants in the case of some semiconductors, very low diffusion coefficient of potential dopants in some semiconductors, very high temperature  needed to render dopants electrically active, or in other words ionization temperature, and also inadequate thermal and structural robustness of many compound semiconductors which makes implementation of selective doping by either ion implantation or diffusion not practical. 


To be continued….

Posted by Jerzy Ruzyllo at 08:02 PM | Semiconductors | Link is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.

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