Which of the following statements concerning depletion region of an unbiased p-n junction diode are true A) The width of the depletion region is independent of densities of dopants B) The width of the depletion region is dependent on the density of dopants C) The electric field in the depletion region is provided by the electrons in conduction band and holes in valency band D) The electric field in the depletion region is produced by the ionized dopent atoms

Options

A. A and B are true
B. B and C are true
C. B and D are true
D. A and C are true

Answer

To determine which statements concerning the depletion region of an unbiased p-n junction diode are true, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** The width of the depletion region is independent of densities of dopants.

**Analysis:** This statement is **false**. The width of the depletion region is indeed dependent on the density of dopants. Higher doping concentrations lead to a narrower depletion region because the electric field created by the ionized dopants is stronger, which pushes the charge carriers further away.

### Step 2: Analyze Statement B
**Statement B:** The width of the depletion region is dependent on the density of dopants.

**Analysis:** This statement is **true**. As mentioned earlier, the width of the depletion region varies inversely with the density of dopants. More dopants lead to a stronger electric field, which results in a narrower depletion region.

### Step 3: Analyze Statement C
**Statement C:** The electric field in the depletion region is provided by the electrons in the conduction band and holes in the valence band.

**Analysis:** This statement is **false**. The electric field in the depletion region is not provided by the free charge carriers (electrons and holes) but rather by the fixed, ionized dopant atoms. The mobile charge carriers are absent in the depletion region as they have recombined.

### Step 4: Analyze Statement D
**Statement D:** The electric field in the depletion region is produced by the ionized dopant atoms.

**Analysis:** This statement is **true**. The electric field in the depletion region arises from the ionized dopant atoms that remain fixed in the lattice after the mobile charge carriers have recombined. This electric field is responsible for the potential barrier in the p-n junction.

### Conclusion
Based on the analysis:
- Statement A: False
- Statement B: True
- Statement C: False
- Statement D: True

Thus, the true statements are B and D.

### Final Answer
The correct statements concerning the depletion region of an unbiased p-n junction diode are:
- B) The width of the depletion region is dependent on the density of dopants.
- D) The electric field in the depletion region is produced by the ionized dopant atoms.