Question

Write a short note on an N-type semiconductor.

Answer 1

Hint: The conduction in the n-type semiconductor can take place as a result of the free electrons represented by the pentavalent impurity atoms. These electrons will be the extra free electrons with respect to the number of free electrons needed to produce the covalent bonds in the semiconductors. This will help you in answering this question.

Complete step by step solution:
When a little amount of Pentavalent Impurities has been added to a pure semiconductor which is giving a large number of free electrons in it, the extrinsic semiconductor developed in this way can be referred to as n−Type Semiconductor. The conduction in the n-type semiconductor is occurring as a result of the free electrons indicated by the pentavalent impurity atoms. These electrons are the extra free electrons with respect to the number of free electrons needed to develop the covalent bonds in the semiconductors. It is produced by the addition of impurity to a pure semiconductor such as silicon or germanium. The impurities which have been used maybe phosphorus, arsenic, antimony, bismuth, or any other chemical compounds. They are known as the donor impurities. They are referred to as a donor impurity as each of the atoms is donating one free electron into the crystal. N means a negative element as the number of free electrons given by the pentavalent impurity is higher than the number of holes. Therefore the question has been answered as required.

Note: In this way, each Arsenic atom will be giving one free electron in the Germanium crystal. As a very small amount of arsenic impurity is added, there will be a large number of atoms. It will be giving millions of free electrons for the process of conduction.