Question

Question 5 (20 points) Saved Where on the periodic table do you find the dopants for silicon? Why?

Answer 1

At standard temperature and pressure, silicon act as a semiconductor. This arises because silicon has a small energy gap between its highest occupied energy levels (the valence band) and the lowest unoccupied ones (the conduction band).The Fermi level is about halfway between the valence and conduction bands and is the energy at which a state is as likely to be occupied by an electron as not. Hence pure silicon is an insulator at room temperature. However, doping silicon with a group 15 elements in periodic table such as phosphorus, arsenic, or antimony introduces one extra electron per dopant and these may then be excited into the conduction band,creating an n-type semiconductor. Similarly, doping silicon with a group 13 element such as boron, aluminium, or gallium results in the introduction of acceptor levels that trap electrons that may be excited from the filled valence band, creating a p-type semiconductor.