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Semiconductor Physics Chapters 1-5
Low temperature: Intrinsic excitation is ignored, impurity ionization dominates, the temperature rises, and the resistivity decreases. Room temperature: All impurities are ionized, lattice scattering dominates, the temperature rises, and the resistivity increases. High temperature: Intrinsic excitation dominates, and the temperature rises. Resistivity drops sharply.
Edited at 2022-11-01 18:09:45- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
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Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
Semiconductor Physics Chapters 1-5
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- One Hundred Years of Solitude Character Relationship Chart
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
- Project Management Process Template
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
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- Outline
Semiconductor Physics
Statistical distribution of carriers in semiconductors
state density
State density is the number of quantum states per unit energy interval around the energy E in the energy band.
Fermi level and statistical distribution of carriers
Fermi level is the highest energy level occupied by electrons in an electronic system at absolute zero.
Carrier concentration of intrinsic semiconductor
Carrier concentration of impurity semiconductor
Impurity energy band In degenerate semiconductors, impurity atoms are relatively close to each other This leads to the overlap of electronic wave functions between impurity atoms, causing the lone The independent impurity energy levels are expanded into energy bands, which are called impurity energy levels.
Degenerate Semiconductor
bandgap narrowing effect
The impurity energy band enters the conduction band or valence band and is connected to the conduction band or valence band, forming a new degenerate energy band, which changes the state density of the energy band, causing the band gap width to decrease from Eg to Eg', so The bandgap becomes narrower when heavily doped.
Freeze-out effect of low-temperature carriers
When the temperature is lower than 100K, the donor impurities are only partially ionized. Some carriers are still frozen at the impurity energy level and do not contribute to conduction.
conductivity of semiconductors
Carrier drift motion and mobility
carrier scattering
Scattering from ionized impurities
hyperbolic trajectory The higher the concentration of ionized impurities, the greater the chance of scattering The higher the temperature, the less likely it is to be scattered by impurities
Scattering of lattice vibrations: only affects long-wavelength phonons
Sound scattering: elastic scattering
Long wave: 10E-8m (spacing of dozens of atoms) Longitudinal waves in long waves play a major role, causing the bandgap width to change. transformation and additional potential fields The higher the temperature, the higher the probability of scattering
Light wave scattering: inelastic scattering
Mainly reflected in ionic crystals Longitudinal optical waves, optical phonons The displacement of positive and negative ions creates an additional potential field The effect is very small at low temperatures; as the temperature rises, the probability increases rapidly
Other scattering
Equivalent energy valley scattering
Long acoustic wave scattering: elastic scattering Long optical wave scattering: inelastic scattering Valley scattering is very small at low temperatures
Scattering from neutral impurities
Scattering from unionized neutral impurities Low temperature works Heavily doped semiconductor
Dislocation scattering: dislocation additional potential field
Alloy Scattering: Compound Semiconductors
Mobility as a function of magazine concentration and temperature
High-purity samples: lattice scattering is dominant, the temperature increases, and the mobility is rapid reduce
Impurity samples: At low temperatures, impurity scattering is dominant. As the temperature increases, the mobility slows down. increase slowly Temperature rise: mainly lattice scattering, temperature rise, mobility decline
Minority and Majority Carrier Mobility: Silicon as an Example
Low impurity concentration: electrons have the same mobility as majority and minority carriers is 1330; hole is 495 The impurity concentration increases and the minority and majority carriers of electrons and holes migrate
The difference in mobility between minority carriers and majority carriers at the same concentration changes with the impurity concentration increase to increase
Resistivity and its relationship to impurity concentration and temperature
Low temperature: Intrinsic excitation is ignored, impurity ionization dominates, and the temperature rises High, resistivity decreases Room temperature: All impurities are ionized, lattice scattering dominates, and the temperature rises High, resistivity increases High temperature: intrinsic excitation dominates, the temperature rises, and the resistivity drops sharply drop
The higher the impurity concentration, the smaller the resistivity
non-equilibrium carriers
Injection and recombination of non-equilibrium carriers
Definition: Carriers in non-equilibrium states such as illumination or electron injection
Lifetime of non-equilibrium carriers
Non-equilibrium carrier lifetime: non-equilibrium carrier concentration The time experienced by Xin Xiaoguo R/e
Quasi-Fermi level
Dynamic changes of Fermi level in non-trivial states
composite theory
According to process
Direct recombination: direct recombination between conduction band and valence band
Indirect recombination: recombination center at the energy level in the forbidden band region
According to the composite position
surface composite
Compounding in vivo
According to the way of releasing energy
Emitting photons: radiative recombination Emitting phonons: energy transferred to lattice vibrations Auger recombination: transfer of energy to other carriers
trap effect
Electron trap: Energy levels above the Fermi level, beyond The closer to the Fermi level, the more significant the trap effect becomes.
Hole trap: energy level below the Fermi level, beyond The closer to the Fermi level, the more significant the trap effect becomes.
Diffusion of carriers
Non-equilibrium download current concentration difference
Diffusion length: the average distance that non-equilibrium carriers travel deep into the sample
Diffusion coefficient: The current value of carrier movement in the presence of a concentration gradient
Drift diffusion of carriers
Einstein's relation: quantitative relationship between diffusion coefficient and mobility
continuity equation
Impurity and defect energy levels in semiconductors
Impurity levels in silicon and germanium crystals
According to the way impurities enter the semiconductor
According to the conductivity type of semiconductor affected by impurities
donor impurity
Donor impurities release electrons, i.e. provide electrons to the guide band When the donor is in the ionized state, it becomes a positively charged center · Group V elements can release electrons when ionized in silicon and germanium Produce conducting electrons and form a positive center, which is called such impurity It is a donor impurity or an n-type impurity. The donor ionization energy is ΔED Donor energy level - the energy of an electron bound by a donor impurity Quantitative state, recorded as ED. Usually at room temperature, impurities can be fully ionized. Electronic concentration The degree is equal to the impurity concentration. n-type semiconductor: a semiconductor that mainly relies on conduction band electrons to conduct electricity body.
acceptor impurity
The process by which acceptor impurities release holes, i.e. provide holes to the valence band hole. When the acceptor impurity is in the ionized state, it becomes a negatively charged center The l|| group elements can accept electrons when ionized in silicon and germanium. Produce conductive holes and form negative electric centers, which are called such impurities is an acceptor impurity or p-type impurity The acceptor ionization energy is ΔEA Acceptor energy level - the energy of a hole bound by an acceptor impurity Quantitative state, recorded as EA. At room temperature, the acceptor impurity is completely ionized, then the hole concentration equal to the acceptor impurity concentration. p-type semiconductor: a semiconductor that mainly relies on valence band holes to conduct electricity body.
Impurity energy levels in III-V compounds
isoelectronic impurities
Impurity atoms often replace atoms with similar electronegativities or similar atomic radii. matrix atoms.
isoelectron trap
Due to differences in electronegativity, some compound semiconductors Electronic impurities can still capture carriers and become charged centers 1. Only when the incorporated atoms and the host crystal atoms are in electronegativity, Isoelectricity can only be formed when there is a large difference in covalent radii. sub-trap 2. The smaller the atomic number of elements in the same family, the greater the electronegativity, and the covalent The smaller the radius, if the impurity electronegativity is greater than the host crystal atoms When, the captured electron becomes a negative center after substitution, otherwise the captured electron becomes a negative center. The hole becomes a positively charged center 3. After the electron trap is charged, it can be captured by Coulomb force. Another type of carrier with the opposite sign, forming a bound exciton, can To improve the optical properties of indirect band gap semiconductor materials.
impurity bisexuality
Doping group VA elements into III-V compound semiconductors such as: Silicon may act as both a donor and an acceptor.
Defect, dislocation energy level
point defect
Frenkel defect - vacancies and interstitial atoms appear in pairs; Schottky defect - only vacancies are formed within the crystal without gaps Atomic defects
Dislocation
At the location of the dislocation, there is an unpaired electron (unsaturated Covalent bond): If it acquires an electron, it acts as an acceptor; if Losing one valence electron will act as a donor. The lattice around the dislocation is distorted and the periodic potential field is broken Bad, causing changes in the energy band structure, leading to band deformation, lattice The bandgap width in the stretching region decreases, and the bandgap width in the lattice compression region becomes big
other
There are four unpaired electrons around the vacancy in Si and Ge, so Vacancies exhibit acceptor action; there are four per interstitial atom electrons that can be lost, so the interstitial atom exhibits a donor effect When M is an interstitial atom, it is a donor, and when X is an interstitial atom, it is an acceptor. The positive ion vacancy VM is the acceptor, and the negative ion vacancy VX is donor. The weakly ionic binary compound AB, the substitution atom AB is the acceptor The master, BA is the donor, forming an anti-structural defect.
Electronic states in semiconductors
Lattice structure and bonding properties of semiconductors
Characteristics of crystal structure
periodic arrangement
fixed melting point
Single product anisotropy
Lattice ten primitives
unit cell
primitive cell
Primitives can have multiple atoms
Crystal orientation and planes
Electronic states and energy bands in semiconductors
Free electron potential field = 0, wave function, energy continuous
Periodic potential field of electrons in crystals, single electron approximation, bloch wave function
Band
Movement of electrons in semiconductors Effective mass
The conductive mechanism of intrinsic semiconductors is holes.
cyclotron resonance
anisotropy
isotropic
Band structure of silicon and germanium