Question

At absolute zero, a p-type semiconductor has-
1. same number of holes and free electrons
2. few holes but no free electrons
3. few holes and few free electrons
4. no charge carriers

Answer 1

Correct Answer - Option 2 : few holes but no free electrons

The correct answer is option 2) i.e. few holes but no free electrons

CONCEPT:

• Semiconductors: Semiconductors are materials that have conductivity between conductors and that of insulators.
  • The missing electrons (holes) are the positively charged particles whereas electrons are the negatively charged particles in a semiconductor. The electrons and holes have an equal magnitude of charge but opposite polarity.
• The conductivity of semiconductors is improved by adding suitable atoms called impurities and this process is called doping.
  1. ​A p-type semiconductor is a semiconductor doped with atoms with three valence electrons which forms a covalent bond with the semiconductor and leaves behind a hole.
  2. An n-type semiconductor is a semiconductor doped with atoms with five valence electrons which form four covalent bond with the semiconductor and leaves behind an extra electron.

EXPLANATION:

• At absolute zero or 0 K, the electrons in the valence band do not have sufficient energy to jump into the conduction band.
• A p-type semiconductor has an acceptor level close to its valence band.
• At 0 K, few electrons from the valence band will be capable of jumping from the valence band to the acceptor level.
• This creates few holes in the valence band, but there will be no free electrons.