Intrinsic and  Extrinsic Semiconductors 

 Theory of Semiconductors

Definition of Semiconductor

It is the definition of the semiconductor may be as follows.The materials that ar neither conductor nor material with an energy gap of concerning one electron volt (electron volt) ar known as semiconductors.
Most common form of materials that ar commercially used as semiconductors ar semiconductor (Ge) and Si (Si) thanks to their property to face up to warmth. meaning there'll be no important amendment in energy gap with ever-changing temperature. The relation between energy gap and temperature for Si and Gear given as, Where, T = temperature in oK
 each Si and Gear parts of IV cluster i.e. each parts have four valence electrons. each kind the bond with the neighbouring atom. At temperature each behave as material i.e. the valence band is full whereas physical phenomenon band is empty however because the temperature is raised a lot of and a lot of valence bonds break and electrons ar released and jump to the physical phenomenon band.

Intrinsic Semiconductors

As per theory of semiconductor, the semiconductor in its pure kind is named as an intrinsic semiconductor. In pure semiconductor variety of electrons (n) is adequate to a variety of holes (p) and so conduction is incredibly low as valence electrons are valence secured. during this case, we tend to write n = p = nickel, wherever nickel is named the intrinsic concentration. It may be shown that nickel may be written wherever, n0 may be a constant, T is that the temperature, VG is that the semiconductor bandgap voltage and Green Mountain State is that the thermal voltage.
The thermal voltage is expounded to the temperature by Green Mountain State = kT/q
Where, k is that the Ludwig Boltzmann constant (k = one.381 × ten − twenty-three J/K).
In intrinsic semiconductors, conduction (σ) is set by each electron (σe) and holes (σh) and depends on the carrier density.
                      σe = neμe,
                       σh = peμh
                        N = n = pe
                     
Conductivity,
                    Where n, p = numbers of electrons and holes severally.
                      μe = quality of free holes and electrons severally
                                         
                       N= charge on carrier

Extrinsic Semiconductors

As per theory of semiconductor, impure semiconductors are referred to as inessential semiconductors. an inessential semiconductor is created by adding a little quantity of impurity. reckoning on the sort of impurity side we've got 2 sorts of semiconductors: N-type and P-type semiconductors. In a hundred million components of semiconductor one, a part of impurity is side.
N sort Semiconductor
In this variety of semiconductor, majority carriers are electrons and minority carriers are holes. N - sort semiconductor is created by adding powerfulness (five valence electrons) impurity in a pure semiconductor crystal
  e.g. P. As, Sb. n sort semiconductor Four of the 5 lepta|electron|negatron} of powerfulness impurity forms a chemical bond with Si atom and also the remaining electron is liberated to move anyplace at intervals the crystal. powerfulness impurity donates negatron to Si that’s why N-type impurity atoms ar referred to as donor atoms. This enhances the conduction of pure Si. Majority carriers are electrons thus conductivity is as a result of these electrons solely and is given by,
                                 σ = neμe