The electron and hole concentration in a
semiconductor in thermal equilibrium is given by
nenh = ni
2
(14 5)
Though the above description is grossly approximate and
hypothetical, it helps in understanding the difference between metals,
insulators and semiconductors (extrinsic and intrinsic) in a simple
manner The difference in the resistivity of C, Si and Ge depends upon
the energy gap between their conduction and valence bands For C
(diamond), Si and Ge, the energy gaps are 5