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반도체 기초 이론 Vol. I Semiconductor Fundamentals by R. F
반도체 기초 이론 Vol. I Semiconductor Fundamentals by R. F. Pierret Modular Series on Solid State Devices 서강대학교 기계공학과 최 범규
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반도체 재료 원소 III-V 화합물 II-VI 화합물 반도체 합금 Si, Ge GaAs, GaP, AlP, AlAs, etc.
ZnO, ZnS, ZnSe, CdS, etc. 합금 AlxGa1-xAs, GaAs1-xPx, etc.
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주기율표와 고체의 분류 주기율표 고체의 분류
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Semiconductor Models Schematic representation of an isolated Si atom
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Semiconductor Models The bonding model Freeing of an electron
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Energy Band Model Conceptual development of the energy band model
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Visualization of carriers
The electron The hole
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Material Classification
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Manipulation of Carrier nos.-Doping(1)
Carrier numbers in intrinsic material n = no. of electrons/cm3 p = no. of holes/cm3 Equilibrium condition No external voltages, magnetic fields, stresses, or other perturbing forces n = p = ni ni = 1×1010/cm3 in Si at room temperature
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Manipulation of Carrier nos.-Doping(2)
Common Si dopants. Arrows indicate the most widely employed dopants Visulization of a donor and acceptor in the bonding model
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Visualization of carriers in the energy band model
Donor Acceptor
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Density of States How many states at any given energy in the bands
gc(E)dE represents the no. of conduction band states/cm3 lying in the energy range between E and E+dE
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The Fermi Function The probability that an available state at an energy E will be occupied by an electron EF = Fermi energy or Fermi level k = Boltzmann constant (8.62E-5 eV/K) T = temperature in Kelvin (K)
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Distribution of Carriers
n type p type
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Carrier Concentrations
Formulas for n and p Nondegenerate semiconductor
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Carrier Concentration Calculations
Charge Neutrality Relationship charge/cm3 Formulas for n and p
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Special cases for semiconductors
Intrinsic semiconductor (NA= 0, ND= 0) Doped semiconductor with Doped semiconductor with Compensated semicond. Intrinsic-like material by making ND - NA = 0 When NA and ND are comparable & nonzero, the material is “compensated”.
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Carrier Action The three primary action
drift: charged-particle motion in response to an applied electric field diffusion: process whereby particles tend to spread out as a result of their difference of concentrations recombination-generation: Generation is a process whereby carriers are created. Recombination is a process whereby carriers are destroyed.
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Drift Current Hole drift current
vd: drift velocity Hole mobility, mp, is the proportional constant between vd and e Current density
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Diffusion Currents Diffusion coefficients Total carrier currents
DP, DN are proportional constants Total carrier currents Visualization of diffusion hole electron
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Recombination-generation
Indirect thermal R-G bonding model energy band model Direct thermal R-G
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