Question

Why does the impurity-doped silicon act as a semiconductor?

Answer 1

1. Impurity-doped silicon acts as a semiconductor because the addition of impurities introduces free charge carriers, significantly increasing its electrical conductivity.
2. In n-type doping, a Group 15 element like phosphorus (P) or arsenic (As), which has 5 valence electrons, is added to silicon. This extra electron becomes a free charge carrier, enhancing conductivity.
3. In p-type doping, a Group 13 element such as boron (B) or aluminium (Al), which has 3 valence electrons, is added to the silicon structure, creating “holes” that act as positive charge carriers.
4. This controlled doping makes silicon a good semiconductor, widely used in transistors, diodes, and integrated circuits.