# When do the holes in semiconductor appear?

I'm trying to understand the concept of semiconductors, as far as I know whenever an electron moves it leaves a hole, so how can we say (for example) that n-type semiconductor has a majority of $e^-$, won't every electron let a hole?

• No, because that's not how a hole is defined. A hole is a vacancy in the valence orbital resulting from having fewer electrons than a full orbital. – Ignacio Vazquez-Abrams Oct 3 '16 at 12:32
• See the picture of the lattice structure at hyperphysics.phy-astr.gsu.edu/hbase/solids/dope.html – Peter Smith Oct 3 '16 at 12:36
• An n-type semiconductor has extra electrons only because it is doped with materials which by nature have more than 4 electrons to make bonds with in their normal states. Since silicon can only make four bonds, and these dopant atoms are forced into a silicon structure, their 5th electron has nothing to make a stable bond with, and so it floats about the lattice - free to drift under the influence of electric fields and contribute to conduction. – jbord39 Oct 6 '16 at 23:53