Classify the following semiconductors as n-type or p-type. (a) Si doped with In (b) Ge doped with Sb (c) Gray Sn doped with As

Doping is the intentional introduction of impurities into a semiconductor to modify its electrical properties. By adding specific elements, the number of charge carriers (electrons or holes) can be increased, enhancing conductivity. N-type doping introduces extra electrons, while p-type doping creates holes by accepting electrons.

N-type semiconductors are created by doping a pure semiconductor, like silicon (Si) or germanium (Ge), with elements that have more valence electrons than the semiconductor itself, typically from group V of the periodic table. This results in an excess of electrons, which are the majority charge carriers, leading to increased conductivity.

P-type semiconductors are formed by doping a semiconductor with elements that have fewer valence electrons, usually from group III of the periodic table. This creates 'holes' or vacancies where an electron is missing, making holes the majority charge carriers. The presence of these holes allows for electrical conduction through the movement of positive charge.