Distinguish between n-type and p-type semiconductors

Semiconductors are the materials which possess a conductivity between conductors (generally metals) and non-conductors or insulators (such ceramics). Semiconductors can be compounds such as gallium arsenide or pure elements, such as germanium or silicon. Physics explains the theories, properties and mathematical approach governing semiconductors.

N-Type semiconductor

When a tetravalent atom such as Si or Ge is doped with a pentavalent atom, it holds the position of an atom in the crystal lattice of the Si atom. The four of the electrons of the pentavalent atom bonds with the four adjoining silicon atoms and the fifth one remains weakly bound to the parent atom. As a result of this, the ionization energy needed to set the fifth electron free is very less and the electrons become free to move in the lattice of the semiconductor. Such semiconductors are termed as n-type semiconductors.

Properties of N-Type semiconductor

  • Mainly due to electrons
  • Completely neutral
  • I = Ih and nh >> ne
  • Majority – Electrons and Minority – Holes

P-Type semiconductor

When a tetravalent atom such as Si or Ge is doped with a trivalent impurity such as Al, B, In, etc., the dopant atom has one less electron than the surrounding atoms of Si or Ge. Thus, the fourth atom of the tetravalent atom is free and a hole or a vacancy is formed in the trivalent atom. In such materials, the holes are the charge carriers and such semiconductors are termed as p-type semiconductors.

Properties of P-Type semiconductor

  • Mainly due to holes
  • Entirely neutral
  • I = Ih and nh >> ne
  • Majority – Holes and Minority – Electrons

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