Question

Describe the nature of electrical conduction in

(a) silicon doped with phosphorus and

(b) indium antimonide doped with zinc.

Short answer

a. The conduction is n-type.

Step-by-step solution

a. Semiconductor

The substances whose conductivity is in between conductors and insulators are called semiconductors. For example, silicon.

Doping

Silicon in very high purity is said to display its intrinsic properties. When certain other elements are added to pure silicon in a process called doping, it acquires interesting electronic properties.

Explanation

For example, if atoms of a Group V element such as phosphorus or arsenic or antimony are diffused into silicon, they substitute for Si atoms in the network. Such atoms have five valence electrons, so each introduces one more electron into the silicon crystal than is needed for bonding. The extra electrons occupy energy levels just below the lowest level of the conduction band.

Little energy is required to promote electrons from such a donor impurity level into the conduction band, and the electrical conductivity of the silicon crystal is increased without the necessity of increasing the temperature. Silicon doped with atoms of a Group V element is called an n-type semiconductor to indicate that the charge carrier is negative