Effect of Temperature on Carrier Transport

EFFECT OF TEMPERATURE ON CARRIER TRANSPORT 

Conductors

In conductors, when temperature is increased, the lattice vibration increases, which causes increased scattering and hence the mobility and conductivity decreases [σ ∞ 1/T].

So, conductors have positive temperature coefficient of resistance i.e., [ρ ∞ T].

Intrinsic semiconductors

In intrinsic semiconductors, when temperature is increased, more numbers of charge carriers both electrons and holes contributes for current. Therefore the conductivity increases with the increase in temperature. [i.e., σ ∞ T].

So, we can say that intrinsic semiconductors is said to have negative temperature coefficient of resistance [ρ ∞ 1/T].

Extrinsic semiconductors

At normal temperature an extrinsic semiconductor will behave as a conductor. When the temperature is increased, since most of the dopant atoms are already ionised, the scattering increases and causes the conductivity to decrease.

However, at transition temperature, the generation of electron-hole pair increases the conductivity.

Thus an extrinsic semiconductor will have positive temperature coefficient at normal temperature and changes to negative temperature coefficient at transition temperature.