Depletion layer has (for an unbiased PN junction) -

Options

A. Electrons
B. Holes
C. Static ions
D. Neutral atoms

Explanation

To solve the question regarding the characteristics of the depletion layer in an unbiased PN junction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the PN Junction**:
- A PN junction is formed when a p-type semiconductor (which has an abundance of holes) is joined with an n-type semiconductor (which has an abundance of electrons).

2. **Formation of the Depletion Layer**:
- When the p-type and n-type materials are brought together, electrons from the n-side will diffuse into the p-side, and holes from the p-side will diffuse into the n-side due to the concentration gradient.

3. **Ionization and Creation of Static Ions**:
- As electrons move from the n-side to the p-side, they recombine with holes, leading to a lack of free charge carriers in the vicinity of the junction. This results in the formation of positively charged ions on the n-side (where electrons left) and negatively charged ions on the p-side (where holes left).

4. **Electric Field Generation**:
- The movement of charge carriers creates an electric field across the junction. This electric field opposes further diffusion of electrons and holes, establishing a potential barrier.

5. **Characteristics of the Depletion Layer**:
- The region around the junction where these static ions exist and where there are no free charge carriers (electrons or holes) is called the depletion layer. This layer is characterized by the presence of static ions (charged ions that cannot move) and is devoid of free charge carriers.

6. **Conclusion**:
- Therefore, in an unbiased PN junction, the depletion layer primarily consists of static ions, which are formed due to the recombination of electrons and holes.

### Final Answer:
The depletion layer has static ions.

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