Statement I: When a semiconductor is doped with a donor impurity, the hole concentration decreases a

Question

Statement I: When a semiconductor is doped with a donor impurity, the hole concentration decreases and the electron concentration increases. \ Statement II : A donor impurity is an atom with valence electrons of five always.

Professor PC Thomas Classes · Answer

(a) : When a semiconductor is doped with a donor impurity (i.e. the impurity atoms have five valence electrons), the four of the five valence electrons form covalent bonds with the four electrons of semiconductor, while the fifth electron is free and increase the electron concentration in the semiconductor. These semiconductors are called $n$-type semiconductor. But if the semiconductor is doped with an atom having three valence electrons, then concentration of hole is more the concentration of electron. These semiconductor are called $p$-type semiconductors or semiconductor with acceptor impurity.