Solids exhibit an amazing range of electrical conductivities, extending over 27 orders of magnitude ranging from 10^–20 to 10⁷ ohm^–1 m^–1.

Solids can be classified into three types on the basis of their conductivities.

(i) Conductors: The solids with conductivities ranging between 10⁴ to 10⁷ ohm^–1m^–1 are called conductors. Metals have conductivities in the order of 10⁷ ohm^–1m^–1 are good conductors.

(ii) Insulators: These are the solids with very low conductivities ranging between 10^–20 to 10^–10 ohm^–1m^–1.

(iii) Semiconductors: These are the solids with conductivities in the intermediate range from 10^–6 to 10⁴ ohm^–1m^–1.

What is the effect on Electrical conductivity of semiconductors when there is a rise in temperature?

Electrical conductivity increases

The correct answer is option 1. Electrical conductivity increases. 

Here is a explanation of how the electrical conductivity of semiconductors changes with temperature:

1. Intrinsic Semiconductors:

Intrinsic semiconductors are pure semiconducting materials with no intentional impurities. At absolute zero temperature (0 Kelvin), intrinsic semiconductors behave as insulators because the valence band is completely filled, and the conduction band is completely empty. As the temperature increases, thermal energy provides enough energy to some electrons in the valence band to overcome the band gap and move to the conduction band. This process generates electron-hole pairs. These thermally generated electron-hole pairs act as charge carriers and contribute to the electrical conductivity of the material. Therefore, as the temperature rises, the number of charge carriers increases, leading to higher electrical conductivity.

2. Extrinsic Semiconductors:

Extrinsic semiconductors are doped semiconductors where impurity atoms are intentionally added to the crystal lattice. Doping introduces additional energy levels within the band gap, creating donor or acceptor levels. At low temperatures, most of the dopant atoms are ionized, contributing additional charge carriers to the material. As the temperature increases, more dopant atoms become ionized due to thermal excitation, leading to an increase in the concentration of charge carriers. Therefore, in extrinsic semiconductors as well, the electrical conductivity increases with temperature due to the increased concentration of charge carriers.

3. Temperature Dependence:

The relationship between electrical conductivity and temperature in semiconductors is not linear but follows a characteristic behavior described by the temperature dependence of carrier concentration and mobility. However, in general, as the temperature increases, the electrical conductivity of semiconductors tends to increase due to the increased concentration of charge carriers.

In summary, the electrical conductivity of semiconductors typically increases with temperature due to the increased generation or ionization of charge carriers, both in intrinsic and extrinsic semiconductors. This behavior is a fundamental characteristic of semiconductor materials and has significant implications for their use in various electronic devices and applications.