Fermi Level in Extrinsic Semiconductor: The equation for f(E) specifying the fraction of all states at energy E (electron volts) occupied under conditions of thermal equilibrium is called the Fermi-Dirac probability function and is given as where k is Boltzmann constant in eV/K, T is temperature in K and EF is the Fermi level or […]
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Carrier Concentration in Intrinsic Semiconductor: For determination of the conductivity of a semiconductor, it is essential to know the Carrier Concentration in Intrinsic Semiconductor of free electrons in conduction band and concentration of holes in valence band. Number of Electrons in the Conduction Band: The product of the number of existing states at any energy
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Explain Conduction in Intrinsic Semiconductors: Explain Conduction in Intrinsic Semiconductors – As already explained, conduction through a semiconductor is due to two mechanisms viz. drift and diffusion. The movement of charge carriers (electrons and holes) under the influence of an applied electric field E is termed as the drift current. The conductivity of σe of
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Explain Conductivity of Metals: Conductivity of Metals – Consider a conductor of length l metres and cross-sectional area A square metres, as shown in Fig. 6.27. Let the number of free electrons available per m3 of the conductor material i.e., electron density be n and E be the applied electric field. Due to the applied
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Relaxation Time, Collision Time and Mean Free Path: The relaxation time is closely related to the mean time of flight between collision and also to the mean free path of the conduction electrons, which is the average distance of undisturbed motion between collision. All the collision processes occurring in the electron gas may be explained
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Charge Densities in Extrinsic Semiconductor: Charge Densities in Extrinsic Semiconductor – Equation (6.19) provides relationship between the electron and hole concentrations n and p respectively. If ND is the concentration of donor atoms, there will be ND immobile positive charges per unit volume contributed by donor ions as the donor atoms are ionized. The positive
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Mass Action Law in Semiconductor: As already mentioned, concentration of free electrons and holes is always equal in an intrinsic semiconductor. When N-type impurity is added to an intrinsic semiconductor, the concentration of free electrons is increased (or the concentration of holes is reduced below the intrinsic value). Similarly addition of P-type impurity results in
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What is Extrinsic Semiconductor? Intrinsic (or pure) semiconductor by itself is of little significance as it has little current conduction capability at ordinary room temperature. However, the electrical conductivity of intrinsic semiconductor can be increased many times by adding very small amount of impurity (of the order of one atom per million atoms of pure
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What is Intrinsic Semiconductor? An intrinsic semiconductor is one which is made of the semiconductor material in its extremely pure form. A semiconductor is not truly intrinsic unless its impurity content is less than one part in 100 million parts of semiconductor. In fact, recent advances have reduced impurity levels in the pure material to
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Fermi Dirac Function in Semiconductor: It is important to know what energies are possessed by a mobile carrier in a solid or semiconductor. This relationship is referred to as energy distribution function. We are concerned with the distribution of energy of the free electrons in a metal. The Fermi Dirac Function statistics enables us to
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