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

Options

A. p- type semiconductor
B. n- type semicondutor
C. intrinsic semiconductor
D. insulation

Explanation

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

### Step 1: Understand the properties of silicon
Silicon (Si) is a semiconductor with four valence electrons in its outer shell. This allows it to form covalent bonds with other silicon atoms, creating a crystalline structure.

**Hint:** Remember that the number of valence electrons determines how an element interacts with impurities.

### Step 2: Identify the type 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 doping:** Involves adding electron-rich impurities (e.g., phosphorus, arsenic) that have more than four valence electrons.
- **P-type doping:** Involves adding electron-deficient impurities (e.g., boron) which have fewer than four valence electrons.

**Hint:** Think about whether the impurity has more or fewer valence electrons than silicon.

### Step 3: Determine the effect of electron-rich impurities
When silicon is doped with an electron-rich impurity like arsenic (which has five valence electrons), the extra electron from the impurity does not participate in bonding. This extra electron becomes available for conduction, enhancing the electrical conductivity of the silicon.

**Hint:** Focus on how the extra electrons contribute to the conduction process in semiconductors.

### Step 4: Classify the type of semiconductor formed
Since the doping introduces extra electrons, the resulting semiconductor is classified as an **n-type semiconductor**. This is because the majority charge carriers in n-type semiconductors are electrons.

**Hint:** Recall that n-type semiconductors are characterized by an abundance of electrons, while p-type semiconductors have an abundance of holes.

### Step 5: Eliminate other options
- **P-type semiconductor:** Formed with electron-deficient impurities, not applicable here.
- **Intrinsic semiconductor:** Refers to pure silicon without any doping.
- **Insulator:** Materials that do not conduct electricity, which does not apply to doped silicon.

**Hint:** Review the definitions of each term to ensure clarity on why they do not apply.

### Conclusion
Silicon doped with an electron-rich impurity forms an **n-type semiconductor**.

**Final Answer:** n-type semiconductor

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