Virtual Labs

Electrical Properties of pn Junction in Depletion Mode

1. What is the effect of forward bias on the depletion region of a pn junction?

a: It increases the depletion width. Explanation

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b: It decreases the depletion width. Explanation

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c: It has no effect on the depletion width. Explanation

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d: It makes the depletion width constant. Explanation

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2. In the context of pn junctions, what does the term 'band bending' refer to?

a: The curvature of the conduction band only. Explanation

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b: The curvature of the valence band only. Explanation

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c: The change in energy levels across the junction. Explanation

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d: The alignment of energy bands at the junction. Explanation

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3. Which of the following is true about the potential difference across the depletion region under equilibrium?

a: It is zero. Explanation

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b: It is equal to the applied bias voltage. Explanation

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c: It is equal to the built-in potential. Explanation

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d: It varies linearly. Explanation

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4. What happens to the minority carrier concentration at the edges of the depletion region in a forward-biased pn junction?

a: It remains constant. Explanation

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b: It decreases. Explanation

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c: It increases. Explanation

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d: It becomes zero. Explanation

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5. In a reverse-biased pn junction, what is the dominant current mechanism?

a: Drift current of majority carriers Explanation

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b: Diffusion current of majority carriers Explanation

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c: Drift current of minority carriers Explanation

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d: Diffusion current of minority carriers Explanation

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6. What is the main reason for the increase in the depletion width under reverse bias?

a: Increased carrier generation. Explanation

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b: Increased carrier recombination. Explanation

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c: Increased electric field. Explanation

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d: Increased doping concentration. Explanation

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7. Which of the following expressions correctly represents the built-in potential (V_bi) for a pn junction?

a: V_bi = kT/q ln(N_A N_D/n_i^2) Explanation

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b: V_bi = kT/q ln(N_A N_D) Explanation

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c: V_bi = q/kT ln(N_A N_D/n_i^2) Explanation

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d: V_bi = kT/q (N_A N_D/n_i^2) Explanation

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8. What does the term 'space charge region' refer to in a pn junction?

a: The neutral region outside the depletion width. Explanation

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b: The region with significant free carriers. Explanation

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c: The depletion region with immobile ionized donor and acceptor atoms. Explanation

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d: The region with constant potential. Explanation

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9. In a pn junction, what is the relationship between the electric field and the distance within the depletion region?

a: The electric field is constant throughout the depletion region. Explanation

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b: The electric field increases linearly with distance. Explanation

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c: The electric field decreases linearly with distance. Explanation

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d: The electric field is zero throughout the depletion region. Explanation

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10. How does the recombination rate of electrons and holes in the depletion region of a pn junction compare to that in the neutral regions?

a: It is higher in the depletion region. Explanation

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b: It is lower in the depletion region. Explanation

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c: It is the same in both regions. Explanation

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d: It varies randomly. Explanation

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