Degenerate n-Type Semiconductor: In a degenerate n-type semiconductor material, where is the Fermi level located?
Electronics and Communication Engineering
Electronic Devices and Circuits
Difficulty: Easy
Choose an option
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Ain the valence band
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Bin the conduction band
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Cat the centre between valence and conduction bands
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Dvery near the valence band
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Eslightly below the conduction band
Answer
Correct Answer: in the conduction band
Explanation
Introduction / Context:Semiconductors can be intrinsic, extrinsic, or degenerate. A degenerate semiconductor is heavily doped so that the Fermi level shifts significantly compared to lightly doped materials.
Given Data / Assumptions:
- Material: degenerate n-type.
- Extremely high donor concentration.
Concept / Approach:
In lightly doped n-type, EF is near conduction band. In degenerate case, EF shifts into the conduction band itself, behaving more like a metal.
Step-by-Step Solution:
Step 1: Normal n-type → EF just below conduction band.Step 2: Degenerate n-type → EF penetrates conduction band.Step 3: Therefore, correct location = conduction band.Verification / Alternative check:
Measured electrical conductivity in degenerate semiconductors supports metallic behavior, consistent with EF inside conduction band.
Why Other Options Are Wrong:
- Valence band: describes p-type or degenerate p-type.
- Centre between bands: intrinsic case.
- Very near valence: wrong polarity.
Common Pitfalls:
- Confusing 'degenerate' with 'intrinsic.'
Final Answer:
in the conduction band