The process of adding impurities to a semiconductor material to increase its conductivity is

1. Analyze the question The question asks for the name of the process in which impurities are deliberately added to a semiconductor (such as silicon or germanium) to increase its conductivity.

2. Explain the concept Pure (intrinsic) semiconductors like silicon have very few free charge carriers at room temperature, so they conduct poorly. To improve this, small amounts of impurity atoms are added in a process called doping. This produces an extrinsic semiconductor.

• n-type semiconductor: Doped with a pentavalent (Group V) element such as phosphorus, arsenic or antimony. Each impurity atom donates an extra free electron, so electrons are the majority carriers.
• p-type semiconductor: Doped with a trivalent (Group III) element such as boron, aluminium or gallium. Each impurity atom creates a "hole" (a missing electron), so holes are the majority carriers.

3. Solve by checking each option

• A. Rectification: Converting alternating current (a.c.) to direct current (d.c.), usually with a diode. It is not about adding impurities.
• B. Emission: The release of electrons from a surface (thermionic, photoelectric emission, etc.). It is not about adding impurities.
• C. Doping: Adding impurities to a semiconductor to increase its conductivity. This matches the question exactly.
• D. Stabilization: Keeping a voltage or current steady (for example with a Zener diode). It is unrelated to adding impurities.

4. Answer The correct option is C. Doping.

5. Exam tip Think of doping as "adding a pinch of spice" to a pure material to change its properties. Remember the pairing: Pentavalent → n-type (extra electrons) and Trivalent → p-type (holes). JAMB often asks follow-up questions on these, so learn them together.