CBSE NOTES CLASS 12 PHYSICS
CHAPTER 14 SEMICONDUCTORS
Extrinsic semiconductor doped with penta-valent impurity like P, As, Sb, Bi, etc in which negatively charged electrons works as charge carriers, is called n-type semiconductor.
The penta-valent foreign atom becomes effectively positively charged when it donates extra electron.
n-type semiconductor the total number of conduction electrons ne is due to the electrons contributed by donors and those generated intrinsically, while the total number of holes nh is only due to the holes from the intrinsic source. But the rate of recombination of holes would increase due to the increase in the number of electrons. As a result, electrons are the majority carriers and holes the minority carriers.