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GATE 2014 EC (EC4) – Question 46

Electronic Devices · Energy Bands and Carrier Concentration · 2 marks · Multiple choice

A uniformly doped N-type semiconductor is biased as shown. E_C is the conduction-band minimum, E_V the valence-band maximum and E_F the Fermi level. Which diagram represents the energy bands?

Diagram for GATE 2014 EC (EC4) question 46
  1. Diagram A
  2. Diagram B
  3. Diagram C
  4. Diagram D

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Show answer and explanation

Correct answer: (D) Diagram D

Explanation

The right contact is at higher electric potential. Electron band energies shift as−qφ, so both conduction and valence band edges slope downward toward the right. Uniform doping keeps their separation and the electron quasi-Fermi-level offset approximately constant. This matches **D**, rather than flat bands or an upward slope.