silicon doped with electron rich impurity forms ………. .

Options

A. p-type semiconductor
B. n-type semiconductor
C. intrinsic semiconductor
D. insulator

Answer

To solve the question "Silicon doped with electron rich impurity forms ……….," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Type of Semiconductor**:
- Semiconductors can be classified into two main types: n-type and p-type.
- N-type semiconductors are formed when a semiconductor (like silicon) is doped with electron-rich impurities, while p-type semiconductors are formed with electron-poor impurities.

2. **Identify the Doping Impurity**:
- The question specifies "electron rich impurity." This refers to impurities that have more valence electrons than silicon (which has four valence electrons).
- Common electron-rich (or n-type) dopants include pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

3. **Determine the Resulting Semiconductor Type**:
- When silicon is doped with these pentavalent impurities, each impurity atom donates an extra electron to the conduction band of silicon, increasing the number of free electrons available for conduction.
- This process leads to the formation of an n-type semiconductor.

4. **Conclusion**:
- Therefore, silicon doped with electron-rich impurities forms an n-type semiconductor.

### Final Answer:
Silicon doped with electron-rich impurity forms an **n-type semiconductor**.