Question

In Si-crystal, impurity donor atom have valency. (A) 2 (B) 3 (C) 4 (D) 5

Short answer

In Si-crystal, impurity donor atoms are typically group V elements, which have a valency of 5. Therefore, the correct answer is (D) 5.

Step-by-step solution

Identify the element group of Silicon

Silicon is a group IV element in the periodic table, which means it has 4 valence electrons. This is important for understanding the valency of impurity donor atoms.

Determine the valency of typical donor impurities in Silicon crystal

Impurity donor atoms in a semiconductor like silicon are typically group V elements (e.g., phosphorus, arsenic, antimony). The reason is that group V elements have 5 valence electrons, one more than group IV semiconductors like silicon. This extra electron becomes available for conduction when the donor atom is introduced into the silicon crystal lattice.

Choose the correct option

Now that we know impurity donor atoms in Si-crystal are group V elements with 5 valence electrons, we can choose the correct option from the given choices. The answer is: (D) 5