Virtual Labs

What does the effective density of states (N_C or N_V) represent in semiconductors?

a: The number of atoms per unit volume Explanation

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b: The number of available energy states near the conduction or valence band edge Explanation

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c: The actual number of free electrons Explanation

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d: The number of ionized donors Explanation

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At room temperature (T = 300K), the thermal energy kT is approximately equal to:

a: 0.0259 eV Explanation

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b: 1.60 eV Explanation

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c: 0.0025 eV Explanation

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d: 9.1 × 10^-31 eV Explanation

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When a semiconductor is doped with donor atoms, what happens to the Fermi level?

a: It shifts closer to the conduction band Explanation

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b: It remains fixed at midgap Explanation

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c: It shifts toward the valence band Explanation

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d: It disappears Explanation

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The expression for intrinsic carrier concentration n_i is given by:

a: n_i = N_C + N_V Explanation

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b: n_i = √(N_C × N_V) exp(-E_g / 2kT) Explanation

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c: n_i = (E_F - E_C) / kT Explanation

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d: n_i = N_D - N_A Explanation

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Which of the following statements is true about extrinsic semiconductors at room temperature?

a: Carrier concentration is dominated by intrinsic carriers Explanation

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b: The Fermi level lies in the middle of the bandgap Explanation

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c: Carrier concentration is primarily determined by dopant atoms Explanation

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d: Effective density of states doesn't matter Explanation

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What is the purpose of plotting n₀, p₀, and n_i against temperature in a semiconductor?

a: To find the bandgap energy directly Explanation

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b: To visualize how mobility changes Explanation

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c: To observe regions of freeze-out, extrinsic, and intrinsic behavior Explanation

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d: To find lattice constant Explanation

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Which condition leads to degenerate semiconductor behavior?

a: Low doping and low temperature Explanation

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b: High doping such that E_F enters conduction band Explanation

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c: Temperature near 0 K Explanation

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d: Complete ionization of dopants Explanation

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In low-temperature regimes, why might ionization of dopants be incomplete?

a: Donors bond with holes Explanation

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b: Donors require thermal energy to release electrons Explanation

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c: Valence band is full Explanation

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d: Electrons have no mass Explanation

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When calculating carrier concentrations in a highly doped material, what statistical model should be used?

a: Boltzmann distribution Explanation

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b: Maxwell-Boltzmann for holes and Fermi-Dirac for electrons Explanation

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c: Fermi-Dirac distribution Explanation

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d: Gaussian distribution Explanation

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Carrier Density