To obtain a `P`-type germanium semiconductor, it must be dopped with

Options

A. phosphorus
B. indium
C. antimony
D. arsenic

Answer

To determine what type of impurity is needed to create a P-type germanium semiconductor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Doping**:
- Doping is the process of adding impurities to a semiconductor to change its electrical properties. There are two types of doping: N-type and P-type.

2. **Identify P-type Semiconductors**:
- A P-type semiconductor is created when a semiconductor material (like germanium) is doped with a trivalent impurity. This means the impurity has three valence electrons.

3. **Determine the Valency of Elements**:
- Trivalent impurities have three valence electrons and can accept an electron, creating 'holes' (positive charge carriers) in the semiconductor.
- Common trivalent elements include Boron (B), Aluminum (Al), and Indium (In).

4. **Analyze the Given Options**:
- The question provides options, and we need to identify which of these is a trivalent element.
- Common pentavalent impurities (which create N-type semiconductors) include Phosphorus (P), Arsenic (As), and Antimony (Sb). These have five valence electrons.

5. **Select the Correct Impurity**:
- Among the options, we look for the trivalent impurity. In this case, Indium (In) is a trivalent element.
- Therefore, doping germanium with Indium will result in a P-type semiconductor.

### Final Answer:
To obtain a P-type germanium semiconductor, it must be doped with **Indium (In)**.

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