Question

The silicon doped with gallium forms

• A. n-type semiconductor
• B. both n and p-type semiconductor
• C. an intrinsic semiconductor
• D. p-type semiconductor

Hint:

Gallium has only three valence electrons, so it creates holes in the silicon lattice.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
Silicon (group 14) has four valence electrons. Doping with an element of a different group changes its conductivity.

Step 2: Effect of gallium
Gallium (group 13) has three valence electrons. Each Ga atom completes only three bonds and leaves a vacancy, called a hole, in the fourth bond.

Step 3: Conclusion
Holes act as positive charge carriers and Ga is an acceptor impurity, so the material is a p-type semiconductor.

Final Answer:
Silicon doped with gallium forms a p-type semiconductor. \[ \boxed{\text{(D) }\text{p-type semiconductor}} \]