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

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.

주기율표와 고체의 분류 주기율표 고체의 분류

Semiconductor Models Schematic representation of an isolated Si atom

Semiconductor Models The bonding model Freeing of an electron

Energy Band Model Conceptual development of the energy band model

Visualization of carriers The electron The hole

Material Classification

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

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

Visualization of carriers in the energy band model Donor Acceptor

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

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)

Distribution of Carriers n type p type

Carrier Concentrations Formulas for n and p Nondegenerate semiconductor

Carrier Concentration Calculations Charge Neutrality Relationship charge/cm3 Formulas for n and p

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”.

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.

Drift Current Hole drift current vd: drift velocity Hole mobility, mp, is the proportional constant between vd and e Current density

Diffusion Currents Diffusion coefficients Total carrier currents DP, DN are proportional constants Total carrier currents Visualization of diffusion hole electron

Recombination-generation Indirect thermal R-G bonding model energy band model Direct thermal R-G