Principle and Working:
The resistivity of Ge crystal is given by ρ=(V/I). 2πs,
Where V is voltage, I is current (mA) and s is spacing between two point electrode.
While the energy band gap is given by Eg =(2k loge r)/T
Where T is absolute temperature & k is Boltzmann constant.
In the present setup, the four probes are placed collinearly with equal spacing between them on the sample. The current is passed through the two outer probes and the potential is measured between the two inner probes.
The errors due to electrical contacts are absent because the current and voltage leads are separate.
