Intrinsic semiconductors

1. A pure semiconductor is called intrinsic semiconductor. It has thermally generated current carriers.
2. They have four electrons in the outermost orbit of atom and atoms are held together by covalent Bond.
3. Free electrons and holes both are charge carriers and n_e(in C.B.) = n_h(in V.B.)

4. The drift velocity of electrons (v_e) is greater than that of holes (v_h)
5. For them fermi energy level lies at the centre of the C.B. and V.B.
6. In pure semiconductor, impurity must be less than 1 in 10⁸ parts of semiconductor.
7. In intrinsic semiconductor

n_e⁽⁰⁾ =n_h⁽⁰⁾=n_i

where,

n_e⁽⁰⁾ = Electron density in conduction band

n_h⁽⁰⁾= Hole density in V.B.

ni = Density of intrinsic carriers

8. The fraction of electrons of valance band present in conduction band is given by f µ = e^–Ee/kT; where E_g = Fermi energy or k = Boltzmann’s constant and T= Absolute temperature.