The conductivity of a pure semiconductor is roughly proportional to T3/2 e–ΔE/2kT where ΔE is the band gap. The band gap for germanium is 0.74 eV at 4 K and 0.67 eV at 300 K. By what factor does the conductivity of pure germanium increase as the temperature is raised from 4 K to 300 K.
Given:
At temperature 4K, E1= 0.74
At temperature 300K, E2=0.67
The conductivity is proportional to T3/2 e–ΔE/2kT,
Let conductivity at 4K be =σ1
and at 300k be = σ2
∴
∴ conductivity increases by the factor of