Question

Pure silicon doped with phosphorus is:
A. Amorphous
B. p-type semiconductor
C. n-type semiconductor
D. Insulator

Answer 1

The doping is the introduction of a new element in a specific structure so that the previous structure formed by the single element can form a combined form of the two elements. The doping needs to be done with an element which can provide the possibility for excess particles to facilitate the flow of charge.

Complete answer: The silicon $\left( {Si} \right)$ is the atom in which the number of valence electrons present is $4$. The phosphorus $\left( P \right)$ is the specific atom which is used for doping the main structure formed by $Si$. Therefore, $Si$ forms four bonds with it which together forms an array. This forms the main structure of silicon with multiple $Si$ atoms joined together like a chain and the branched form. Each of the phosphorus $\left( P \right)$ atoms has $5$ valence electrons, which is why there can be $5$ bonds which can be formed with the $P$. These associations form the bonded structure of different molecules associated with $P$. If doping of Phosphorus takes place with $Si$ then there are $4$ bonds of $Si$ which are involved in forming the association with the $P$ atom. The number of associations of $P$ atom involved in this structure are $4$ which means four valence electrons of $P$ are involved in the association with the $Si$ which together forms the ${\left( {SiP} \right)_n}$ structure. This is a perfectly bonded structure because of the four associations that can form the straight chains and branching structures. But even after the formation of this association, there is an extra valence electron present in each of the $P$ atoms. This extra electron remains in the system and it is the charged particle responsible for conducting electricity. Therefore, the insulator which is formed with $Si$, after doping with $P$ the insulator becomes a semiconductor. Since the negatively charged particle or electron is involved in the flow of electricity, this type of semiconductor is a C. n-type semiconductor.

Hence the correct option is (C).

Note: The semiconductor involves the flow of electrons to a certain limit, which means that the movement of electricity depends on the type of charged particle. The n-type semiconductor is the one which involves excess electrons while the p-type semiconductor involves the use of excess protons in the process of conducting electricity.