Current in Semiconductors

Creation of Electron Hole pairs in a Si crystal

Electron Hole pairs in a Si crystal

Types of current in a pure SemiconductorElectron CurrentHole Current

Electron CurrentIn Intrinsic Si, it is produced by the

movement of thermally generated free electrons

Hole Current in Intrinsic Si

Extrinsic SemiconductorsTwo Types 1. N type Semiconductors 2. P type Semiconductors

N Type SemiconductorPentavalent Impurity Atom in a Si Crystal

Structure

N Type Semiconductor

P Type SemiconductorTrivalent Impurity Atom in a Si Crystal

Structure

P Type Semiconductor

N type & P type Semiconductors

Effect of donor impurities on the Energy Band Structure

Effect of Acceptor impurities on the Energy Band Structure

Change in the Energy band diagram due to doping

Effect of Temperature on Semiconductor Intrinsic SemiconductorAs temp , more electron-hole pairs

are producedConductivity increases with increase in

tempThat is resistivity decreases with increase

in tempHence Semiconductors have –ve temp

coefficient of resistance

Effect of Temperature on SemiconductorP-type Semiconductor???N-type Semiconductor???

Law of Mass ActionUnder Thermal Equilibrium for any semiconductor,

the product of the number of holes and number of electrons is constant & is independent of the amount of donor & acceptor impurity doping

Current Flow Information

Current Flow Information

ReferenceElectronic devices by FloydElectronic devices & circuits by

Salivahanan