Question

Pure silicon does not conduct electricity. How can it be made a conductor of electricity? Explain with examples.

Answer 1

Pure silicon does not conduct electricity effectively because it is a semiconductor with very few free electrons at room temperature. However, its conductivity can be significantly improved through a process called doping. Doping involves adding a small amount of impurity atoms to pure silicon to increase the number of charge carriers (either electrons or holes).

There are two main types of doping:

1. n-type Doping: When silicon is doped with a group 15 element like phosphorus (P) or arsenic (As), each impurity atom contributes an extra electron. These additional electrons are free to move, thus increasing the electrical conductivity. For example, phosphorus-doped silicon becomes an n-type semiconductor, where electrons are the main charge carriers.

2. p-type Doping: When silicon is doped with a group 13 element like boron (B) or aluminium (Al), each impurity atom creates a “hole” by lacking one electron needed for bonding. These holes behave like positive charge carriers. For instance, boron-doped silicon becomes a p-type semiconductor, where holes move and carry current.

By doping pure silicon with such elements, it is transformed into a material that can conduct electricity efficiently, and this principle is the foundation of modern electronic devices like transistors and diodes.