Question

If we mix a pentavalent impurity in a crystal lattice of Germanium, what type of semiconductor formation will occur?
(A) p-type
(B) n-type
(C) Both A and B
(D) None of the above

Answer 1

Hint: Pentavalent impurity has five electrons in its valence shell of electrons. The new material is named after the reason for the enhanced conductivity of the semiconductor element.

Complete step by step solution:
Germanium is an element whose atomic number is 32 and it is a p-block element. Germanium is a metalloid. So, it is a semiconductor element.
- Semiconductor elements are those who have electric conductivity between ${10^{ - 6}}{\text{ to1}}{{\text{0}}^4}oh{m^{ - 1}}{m^{ - 1}}$.
- All the semiconductor elements have a small gap between the valence band and the conduction band. So, some electrons jump to the conduction band and are responsible for the conductivity.
- However, the conductivity of these semiconductor metals is too low for practical usage. So, we need to add some impurity to it and it enhances the conductivity of semiconductor material. This process is called doping.
- We are given that a pentavalent impurity is added to the germanium. Pentavalent atoms have five electrons in their valence shell. Germanium being an element of the carbon family has four electrons in its valence shell.
- So, adding a pentavalent element gives birth to a delocalized electron and other four electrons are used in covalent bonding.
- Here, we can say that the conductivity in that material is due to the extra delocalized electron.

Therefore, germanium doped with pentavalent impurity forms n-type semiconductor.

Note: Remember that elements like Phosphorus (P), Arsenic (Ar) are the examples of pentavalent impurity. Trivalent impurities like Aluminum (Al), and Boron (B) are also available whose doping in semiconductor elements results in the formation of p-type semiconductor.