JEE Main & Advanced Physics Semiconducting Devices 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 \[{{10}^{8}}\] parts of semiconductor.

(7) In intrinsic semiconductor \[n_{e}^{(o)}=n_{h}^{(o)}={{n}_{i}}\]; where \[n_{e}^{(o)}=\] Electron density in conduction band, \[n_{h}^{(o)}=\] Hole density in V.B., \[{{n}_{i}}=\] Density of intrinsic carriers.

(8) The fraction of electrons of valance band present in conduction band is given by \[f\propto {{e}^{-{{E}_{g}}/kT}}\]; where \[{{E}_{g}}=\] Fermi energy or k = Boltzmann's constant and T = Absolute temperature

(9) Because of less number of charge carriers at room temperature, intrinsic semiconductors have low conductivity so they have no practical use.

(10) Number of electrons reaching from valence band to conduction band \[n=A{{T}^{3/2}}{{e}^{-{{E}_{g}}/2kT}}\]