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Lunch break - What element is added to Silicon in the production of transistors to increase the number of free electrons?

13 Jul 2011

eTech Magazine

United Kingdom

What element is added to Silicon in the production of transistors to increase the number of free electrons?

Replies

TechTinkerer

Denmark
44 weeks ago

In theory: Any element that has five valence electrons, rather than the four of silicon: Four of the five valence electrons fill in the roles of making bonds to four neighbouring atoms in the silicon crystal lattice, but the fifth electrons is like a driver looking for an empty space in a brim-filled parking lot -- endlessly going up and down the driveways.

Ioannis Kedros

United Kingdom
44 weeks ago

Hmmm... I am not sure about this one (long time ago since my last physics / chemistry lessons). I know that the process is called doping and they use this process in order to shape the electrical properties of the semiconductor (as it is pure at the beginning).

The materials that you can use are different and depending of the group that the semiconductor belongs. Except from that, you can use acceptors (creating holes) or donors (creating more valence electrons) for the doping. The silicon is on group 14 and I think the answer is Boron and Phosphorus. Probably Arsenic as well... 

LStacey

United Kingdom
44 weeks ago

Hmm, I seem to recall boron being the most common. It was probably even longer ago for me...