Semiconductor Charge Carriers Quiz

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Questions and Answers

Match the following charge carriers with their characteristics in a semiconductor:

Electron = Contributes to the current in the conduction band Hole = Contributes to the current in the valence band Density of electrons = Related to the density of states function and Fermi distribution function Density of holes = Related to the density of states function and Fermi distribution function

Match the following functions with their definitions in a semiconductor:

Electronic density of states = Measure of available energy levels for a carrier Fermi distribution function = Determines density of electrons and holes Effective density of states function = Determines concentration of states per unit energy Thermal equilibrium hole concentration = Expression for the concentration of holes in the valence band at thermal equilibrium

Match the following parameters with their definitions in the context of hole concentration in a semiconductor:

Nν = Effective density of states function in the valence band mₚ⋅∗ = Density of states effective mass of the hole Po = Thermal equilibrium concentration of holes in the valence band KF = Fermi level energy

Match the following temperature-related terms with their significance in semiconductor physics:

T=300 K = Magnitude of Nν for most semiconductors K = Boltzmann constant Thermal equilibrium = State where carriers are in balance with their environment Exp[KT] = Exponential term representing carrier concentration at thermal equilibrium Signup and view all the answers

Match the following physical quantities with their units for semiconductor charge carriers:

Concentration of states per unit energy = States per unit volume per unit energy Density of charge carriers = $10^{19} cm^{-3}$ at T=300 K for most semiconductors Carrier concentration = $N_{ u} exp[KT]$ Effective mass of the hole = Parameter determining density of states effective mass Signup and view all the answers

Match the following equations with their significance in semiconductor physics:

$N_\nu = 2\left(\frac{2\pi m_p^* k T}{h^2}\right)^{3/2}$ = Effective density of states function in the valence band $P_o = N_\nu \exp\left(\frac{E_F - E_\nu}{kT}\right)$ = Thermal equilibrium concentration of holes in the valence band $I = qnAv_d$ = Equation for current in a semiconductor $n_i = \sqrt{N_cN_v}e^{-E_g/2kT}$ = Intrinsic carrier concentration equation Signup and view all the answers

Match the following terms with their descriptions in semiconductor physics:

Electron = One type of charge carrier in a semiconductor Hole = Another type of charge carrier in a semiconductor Density of states function = Measure of energy levels available to a carrier Fermi distribution function = Relates to the density of electrons and holes in a semiconductor Signup and view all the answers

Match the following physical quantities with their significance in semiconductor physics:

Current (I) = Rate at which charge flows in a semiconductor Density of charge carriers = Determines the current in a semiconductor Electronic density of states = Concentration of states per unit energy in a semiconductor Thermal equilibrium hole concentration = Concentration of holes in the valence band at thermal equilibrium Signup and view all the answers

Match the following temperatures with their significance in semiconductor physics:

300 K = Magnitude of Nν for most semiconductors kT = Term appearing in the Fermi distribution function and thermal equilibrium hole concentration equation Room temperature = Typical operating condition for many semiconductor devices Eg/2kT = Term appearing in the intrinsic carrier concentration equation Signup and view all the answers

Match the following formulas with their representations for charge carriers in a semiconductor:

$n_i = \sqrt{N_cN_v}e^{-E_g/2kT}$ = Intrinsic carrier concentration equation $P_o = N_\nu \exp\left(\frac{E_F - E_\nu}{kT}\right)$ = Thermal equilibrium concentration of holes in the valence band $N_\nu = 2\left(\frac{2\pi m_p^* k T}{h^2}\right)^{3/2}$ = Effective density of states function in the valence band $I = qnAv_d$ = Equation for current in a semiconductor Signup and view all the answers

Study Notes

Charge Carriers in a Semiconductor

Electrons: Negatively charged, high mobility, can move freely within the semiconductor
Holes: Positively charged, low mobility, represent the absence of an electron in a covalent bond

Functions in a Semiconductor

Donor: Impurities that release excess electrons, increasing the number of free electrons (n-type)
Acceptor: Impurities that release excess holes, increasing the number of free holes (p-type)

Hole Concentration in a Semiconductor

Hole concentration (p): Number of holes per unit volume of semiconductor material
** Majority carriers**: Holes in p-type semiconductor, electrons in n-type semiconductor
** Minority carriers**: Electrons in p-type semiconductor, holes in n-type semiconductor

Fermi level: Energy level at which the probability of finding an electron is 50%
Intrinsic temperature (Ti): Temperature at which the Fermi level lies at the middle of the bandgap
Debye temperature: Temperature above which the semiconductor exhibits intrinsic behavior

Units for Semiconductor Charge Carriers

Electron concentration (n): Number of electrons per unit volume (m⁻³)
Hole concentration (p): Number of holes per unit volume (m⁻³)

Equations in Semiconductor Physics

Law of Mass Action: np = ni² (relationship between electron and hole concentrations)
Fermi-Dirac distribution: Describes the probability of finding an electron at a given energy level

Terms in Semiconductor Physics

Intrinsic semiconductor: Pure semiconductor material with no impurities
Extrinsic semiconductor: Semiconductor material with impurities (n-type or p-type)
Bandgap energy (Eg): Energy difference between valence and conduction bands

Physical Quantities in Semiconductor Physics

Mobility (μ): Ability of charge carriers to move through the semiconductor material (m²/V·s)
Diffusion coefficient (D): Measure of how quickly charge carriers diffuse through the material (m²/s)

Temperatures in Semiconductor Physics

Room temperature (RT): Temperature at which semiconductor devices typically operate (around 300 K)
Cryogenic temperature: Very low temperature (near absolute zero) used in some semiconductor applications

Formulas for Charge Carriers in a Semiconductor

Electron concentration (n): n = NI * e^(-(Eg/2)/kT)
Hole concentration (p): p = NI * e^((Eg/2)/kT)

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Test your knowledge on the charge carriers in semiconductors. Learn about the role of electrons and holes in contributing to current flow, and the relationship between charge carrier density and semiconductor characteristics.