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Sunday, January 19, 2014

#273 Problems with doping, cont.

Following on my previous comments regarding semiconductor doping, let me be more specific regarding problems with selective, i.e. localized, doping.


Consider, for example, wide-bandgap semiconductors. Diamond, which in theory is the best semiconductor around, is inherently p-type and cannot be readily converted into n-type. In contrast, in silicon carbide, SiC, p-type regions are very difficult to form as neither diffusion nor ion  implantation is effective.  In the former case it is because of extremely low diffusion coefficients of possible p-type dopants such Al  in SiC while in the latter extremely high temperature needed to activate dopants (1500 deg. C and above) is the lim itation. Did you notice that commercial SiC power diodes are based primarily on metal-semiconductor (Schottky) diode and not a p-n junction? Then, there is gallium nitride, GaN, in which n-type doping is simple, but p-type doping is very complicated. 


In general, selective doping of compound semiconductors is a challenge. Hence, when it comes to alterations of the conductivity type/doping level while building III-V electronic or photonic devices the task is typically accomplished by in situ doping during growth of the material rather than by implantation or diffusion into the material already formed.

Posted by Jerzy Ruzyllo at 09:43 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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