N-type Semiconductor
An extrinsic semiconductor in which pentavalent donor impurities create an excess concentration of free electrons as majority charge carriers.
Governing formula
n ≈ N_D ≫ p, n p = n_i²
SI unit
cm⁻³ (Electron Concentration)
In depth
Doping silicon (valence 4) with pentavalent atoms like Phosphorus or Arsenic (valence 5) provides four electrons for covalent bonds, leaving the fifth electron weakly bound. Small thermal energy easily liberates it into the conduction band.
Examples in the real world
Phosphorus-doped silicon forming the n-channel of MOSFET power transistors.