Notes based on “Electronic Principles”, by Malvino
Semiconductors are materials which have a conductivity between conductors and nonconductors or insulators.
Holes are formed when one or more of an element's valence electrons are excited and jump to a higher energy level.
There are two types of semiconductors:
Before looking at the different types of semiconductors, you have to understand doping.
Doping is the process of adding impurities to a semiconductor
Intrinsic semiconductors are those which are not doped, or in other words, are pure.
Extrinsic semiconductors are those which are doped, or in other words, are impure.
It stands for negative type semiconductors. This is where the semiconductor is doped with an element which has one more valence electron. Silicon, for example, can be doped with a pentavalent element like Arsenic or Phosphorus.
What this does is that, after it bonds in a crystal form with the semiconductor, there is an extra electron available. This electron must travel in the conduction band. Thus, there are more electrons in the conduction band. There are less number of holes created as such the electrons are the majority charge carriers and the holes are the minority charge carriers.
The atom used to dope a semiconductor to create a N-type semiconductor is called as a donor atom. It donates the electron to the conduction band.