What is the importance of four valence electrons in semiconductors?
It has to do with the fact that in large numbers, there is metallic bonding and semimetallic bonding. In both of those, electrons are shared among the entire network. In metallic bonding, there is virtually no gap between a band that is full of electrons and a band in which there are no electrons (where the electrons will want to go, and where they will easily be pushed along). In semimetallic bonding, however, there is a small gap between the filled band and the empty band, thus restricting the amount of electrons that will pass through. 4 valence electrons allow for 4 more electrons to pass through, whereas 5 only allows 3 and changes conductivity, and 3 allows 5 which also changes conductivity. Silicon and Germanium (nowadays it’s mostly silicon, but it used to be more germanium) bond semimetallically, whereas carbon tends to form covalent networks rather than bond semimetallically, and tin and lead bond metallically. There is another thing that is used in the making of semiconducto
