Question

On doping Ge metal with a little of In or Ga, one gets

• A. p-type semiconductor
• B. insulator
• C. n-type semiconductor
• D. rectifier

Answer 1

The Correct Option is A

To solve this question, we need to understand the concept of doping in semiconductors:

1. **Definition of Doping**: Doping is the process of adding impurities to a semiconductor to change its electrical properties. Germanium (Ge) is a Group 14 element used as a semiconductor.

2. **Types of Doping**:

• n-type Semiconductors: These are formed by doping Ge with pentavalent elements (Group 15 elements such as phosphorus, arsenic). These elements have one extra electron that is free to move, resulting in increased conductivity.
• p-type Semiconductors: These are formed by doping Ge with trivalent elements (Group 13 elements such as indium (In), gallium (Ga)). These elements have one fewer electron than Ge, creating "holes" or positive charge carriers that increase conductivity.

3. **Application to the Question**: The question asks what happens when Ge is doped with a little amount of In or Ga.

• Both indium (In) and gallium (Ga) are trivalent elements from Group 13.
• When Ge is doped with these elements, it forms a p-type semiconductor because the dopant introduces holes into the semiconductor.

4. **Conclusion**: The correct answer is "p-type semiconductor" since adding In or Ga to Ge creates holes that act as the predominant charge carriers, forming a p-type semiconductor.

5. **Justification for Other Options**:

• Insulator: Doping Ge does not transform it into an insulator; it enhances its conductivity.
• n-type semiconductor: This is formed when Ge is doped with pentavalent elements, which offer extra electrons, not holes.
• Rectifier: A rectifier is a device that converts AC to DC; it is not directly a property of doped Ge.

Therefore, upon doping Ge with In or Ga, we obtain a p-type semiconductor.