Virtual Labs

Density of States

What does the Fermi-Dirac distribution function indicate about electron occupancy?

a: It gives the number of energy states in the conduction band Explanation

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b: It indicates how many holes are present in the valence band Explanation

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c: It gives the probability that a given energy level is occupied by an electron Explanation

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d: It shows the distribution of atoms in a crystal Explanation

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What is the value of f(E) exactly at E = E_F for any temperature T?

a: 0 Explanation

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b: 0.5 Explanation

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c: 1 Explanation

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d: T-dependent Explanation

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Which of the following plots best represents the Density of States (DOS) vs Energy for a 3D semiconductor?

a: A constant flat line Explanation

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b: A decreasing exponential curve Explanation

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c: A curve increasing with square root dependence on energy Explanation

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d: A parabolic increase Explanation

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Why does the Fermi-Dirac distribution differ in metals and semiconductors at room temperature?

a: Metals have a larger bandgap than semiconductors Explanation

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b: Semiconductors have more free electrons at room temperature Explanation

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c: Fermi level lies within a band in metals and in the gap for semiconductors Explanation

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d: DOS is higher in semiconductors Explanation

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What does a higher effective mass imply about the density of states (DOS) in a semiconductor?

a: DOS decreases with higher effective mass Explanation

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b: DOS remains unchanged Explanation

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c: DOS increases because it is proportional to (m*)^3/2 Explanation

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d: DOS depends only on bandgap and not mass Explanation

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How does the product of DOS and f(E) influence carrier distribution in semiconductors?

a: It determines the number of atoms in the crystal Explanation

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b: It gives the effective bandgap Explanation

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c: It defines how carriers are distributed in energy space Explanation

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d: It affects only mobility, not carrier distribution Explanation

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For an n-type semiconductor, how does the Fermi level shift with increasing donor concentration?

a: It moves toward the valence band Explanation

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b: It stays constant Explanation

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c: It shifts upward toward the conduction band Explanation

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d: It moves to mid-gap Explanation

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What is the mathematical expression for the density of states in a 3D semiconductor near the conduction band?

a: D(E) ∝ (E - E_C)^1/2 Explanation

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b: D(E) ∝ (E - E_C) Explanation

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c: D(E) ∝ log(E - E_C) Explanation

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d: D(E) ∝ (E - E_C)^-1 Explanation

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What is the physical meaning of the temperature dependence in the Fermi-Dirac distribution function?

a: It sharpens the distribution as temperature increases Explanation

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b: It broadens the transition between filled and empty states Explanation

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c: It shifts the energy levels Explanation

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d: It reduces the number of energy states available Explanation

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