Question

What is doping? What are n-type and p-type semiconductors?

Answer 1

Doping is the addition of impurities to a semiconductor. Due to this, electrons are added to conduction band. This increase the electrical conductivity.
When group V elements such as phosphorous and arsenic are doped in group IV elements (Si or Ge), n-type of semiconductor is obtained. The electrical conduction is due to extra negative charges due to extra electrons of the impurity.
When group III elements such as boron and gallium are doped in group IV elements (Si or Ge), p-type of semiconductor is obtained. The electrical conduction is due to extra positive charges due to electron holes of the impurity.