What Are The Difference Between Intrinsic And Extrinsic Semiconductor

What Are The Difference Between Intrinsic And Extrinsic Semiconductor

An intrinsic semiconductors is a pure semiconductor , the concentrations of electrons and holes are equal and in intrinsic follow of current is as a result of thermal agitation .

  While an extrinsic semiconductor is an impure semiconductor, can be n-type with electrons as majority carriers or p-type with holes as majority charge carriers.

By What Process Are The Majority Carriers Produced

Majority charge carriers in a semiconductor are produced in a process called doping, there are positive holes in p-type and negative electrons in n-types.

 To produce electrons as majority carriers, an intrinsic semiconductor has to be doped with a donor impurity (pentavalent atoms). This doping will produce an excess of electrons which will act as a majority carriers.

 To produce a hole as a majority carrier we need to use an acceptor dopant or trivalent atoms. P-doping will produce a p-type semiconductor with holes as the majority charge carriers, when a voltage is applied across the semiconductor the majority carriers flow as current.

How Minority Charge Carriers Produced

Minority carriers are not produced in a semiconductors by any “artificial” process. They are inbuilt within the semiconductor.

 In an typical (pure)  semiconductor like silicon or germanium, there are four negative electrons and four positive holes, no majority or minority charge carriers, they have equal concentration.

 To produce a minority carrier, the semiconductor can be doped with either a pentavalent or trivalent atoms, when a semiconductor is doped with a pentavalent atoms, an n-type is produced where electron are the majority carriers and holes are the minority carriers.

While  doping a semiconductor with a trivalent atom will produce p-type semiconductor with holes as a majority carriers and negative electrons as minority carriers.

 Therefore a  minority  carrier are produced through “alternate”  doping( meaning if we want holes as minority carriers we do n-doping).

what do you mean by band gap of a semiconductor?

Band gap is an energy gap where no electrons can reach,  in a semiconductor it is what separate the conduction band and the valence band, it is very wide in insulators ,absent in good conductors and very narrow in semiconductors.

 In semiconductors electrons do not move into the forbidden gap at absolute temperature but can only do so at a temperature below the melting point of the semiconductor.

 For intrinsic semiconductor the band gap determine the conductivity as electrons and holes can only be excited to cross over it. Though the thermal excitation aid the cross over.

If the band energy of a material is above 3ev , it is considered to be an insulator,  the conductivity of an extrinsic semiconductor is depend on the type of doping it has, though high temperature will facilitate fast electron mobility.

do you know the main difference between insulators and semiconductors

 A conductor readily conduct electric current, they have excess free electrons, according to band energy theory;  the conductor, semiconductor and insulator are separated by sort of energy gaps. Namely the conduction band  , valence band  and forbidden gap.

 The conductor has only two energy gaps, the conduction band and the valence band, the two band are merged, electrons flow readily from the conduction band to the valence band .

 In semiconductors three regions exist, the conduction, valence and forbidden gap.  The forbidden  gap is narrowed , a little excitation can bridge the forbidden gap and electrons can easily move from the conduction band to the valence band whereas an insulator has all the three energy band,  but here the forbidden gap is very wide that no amount of thermal excitation can cause electrons to flow from the conduction band  to valence . Therefore the main difference between insulators and semiconductor is that the forbidden gap in  the semiconductor can be bridged while that of insulators cannot be bridged

Ask Question about Semiconductor Doping

briefly explain how n-types are doped

Doping is the addition of impurities to an intrinsic semiconductor to increase its effectiveness. Pentavalent atoms are atoms with five electrons in their outermost shell, when these atoms are added to a semiconductor like silicon and germanium  with only four valence electrons in their outermost shell,  they introduce a free electrons  which are ready to move as electric current when a voltage is applied. therefore  doping a semiconductor with pentavalent impurities results in n-type type semiconductor.

state difference between pentavalent and trivalent impurities

Pentavalent impurities are atoms that create n-type semiconductor, they are atoms with 5 electrons in their outermost electronic shell. Their excess electrons makes the semiconductor to have a free unbound electrons .  These excess electrons makes the semiconductor  to have negative  electrons  as majority carriers where as trivalent element create  p-type extrinsic semiconductor, the impurities “starve” the semiconductor of electrons . They are mostly  metals and attract  the electrons in semiconductors  thereby creating a hole ( empty space)  this increase the tendency of the doped semiconductor  to attract electrons and hence a p-type semiconductor is created.

what are the major importance of doping in semiconductors

 the importance  of doping  is to increase the “effectiveness”  of the a semiconductor, an intrinsic or pure  semiconductor  has equal number of negative electrons and positive holes and their conductivity is rather determined by the thermal agitations or properties of the materials they found themselves.

 therefore dopants increases the conductivity, if they are pentavalent atoms , they do so by introducing free electrons into the semiconductor  while trivalent atoms creates an empty vacancy called a hole, thereby making the semiconductor ready to attract electrons( that is to behave like electronegative atoms)

can you define p-type and n-type semiconductors

An n-type semiconductor has an excess of electrons , this made it ready to donate  the electrons , it has negative electrons as it majority charge carrier. The four electrons of the semiconductor will bond covalently  with four of the five electrons of the pentavalent atoms, the remaining one electron will remain free. When a voltage is applied the electrons will be “readily” to move as electric current .

While p-type semiconductor  has hole as majority carriers the addition of trivalent atoms to  a pure semiconductor will shift the electron to hole concentrations  in a semiconductor . Thereby creating a hole (electrons seeking space)  and hence a p-type is formed