Which statement is/are about extrinsic conductor is true

Options

A. addition of phosphorus as impurities in silicon makes p type semi conductor
B. addition of Al as impurities in silicon makes p type semi conductor
C. in n type semi conductor charge is carried by the hole
D. in p type semi conductor charge is carried by the electron

Answer

To determine which statements about extrinsic conductors are true, we need to understand the concept of extrinsic conductors and the role of doping with impurities. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Extrinsic Conductors
Extrinsic conductors are materials that have been modified to enhance their electrical conductivity by adding impurities. These conductors are typically made from group 14 elements like silicon (Si) or germanium (Ge).

**Hint:** Remember that extrinsic conductors are created by doping pure semiconductors with specific impurities.

### Step 2: Identify the Role of Dopants
When group 14 elements are doped with impurities from group 13 or group 15, they create two types of semiconductors:
- **P-type Semiconductors:** Formed by doping with group 13 elements (e.g., aluminum). These create "holes" in the lattice structure, which act as positive charge carriers.
- **N-type Semiconductors:** Formed by doping with group 15 elements (e.g., phosphorus). These provide extra electrons, which act as negative charge carriers.

**Hint:** Group 13 elements create holes, while group 15 elements provide extra electrons.

### Step 3: Analyze the Statements
Now, let’s evaluate the provided statements one by one:

1. **Statement 1:** Addition of phosphorus as impurity in silicon makes a p-type semiconductor.
- This statement is **false**. Phosphorus is a group 15 element and will create an n-type semiconductor.

2. **Statement 2:** Addition of aluminum as impurity in silicon makes a p-type semiconductor.
- This statement is **true**. Aluminum is a group 13 element and will create a p-type semiconductor.

3. **Statement 3:** In n-type semiconductors, charge is carried by holes.
- This statement is **false**. In n-type semiconductors, charge is carried by electrons.

4. **Statement 4:** In p-type semiconductors, charge is carried by electrons.
- This statement is **false**. In p-type semiconductors, charge is carried by holes.

### Step 4: Conclusion
Based on the analysis of the statements, the only true statement is:
- **Addition of aluminum as impurity in silicon makes a p-type semiconductor.**

**Final Answer:** The correct answer is that the second statement is true.