) At room temperature, most of the acceptor atoms get
ionised leaving holes in the valence band Thus at room temperature the
density of holes in the valence band is predominantly due to impurity in
the extrinsic semiconductor 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