MindMap Gallery carrier transport phenomenon
Study notes on carrier transport phenomena in semiconductors provide you with a clear and comprehensive learning framework. This mind map helps you become familiar with the key points of knowledge and enhance your memory. Students in need can save it.
Edited at 2024-11-23 20:43:10Rumi: 10 dimensions of spiritual awakening. When you stop looking for yourself, you will find the entire universe because what you are looking for is also looking for you. Anything you do persevere every day can open a door to the depths of your spirit. In silence, I slipped into the secret realm, and I enjoyed everything to observe the magic around me, and didn't make any noise. Why do you like to crawl when you are born with wings? The soul has its own ears and can hear things that the mind cannot understand. Seek inward for the answer to everything, everything in the universe is in you. Lovers do not end up meeting somewhere, and there is no parting in this world. A wound is where light enters your heart.
Chronic heart failure is not just a problem of the speed of heart rate! It is caused by the decrease in myocardial contraction and diastolic function, which leads to insufficient cardiac output, which in turn causes congestion in the pulmonary circulation and congestion in the systemic circulation. From causes, inducement to compensation mechanisms, the pathophysiological processes of heart failure are complex and diverse. By controlling edema, reducing the heart's front and afterload, improving cardiac comfort function, and preventing and treating basic causes, we can effectively respond to this challenge. Only by understanding the mechanisms and clinical manifestations of heart failure and mastering prevention and treatment strategies can we better protect heart health.
Ischemia-reperfusion injury is a phenomenon that cellular function and metabolic disorders and structural damage will worsen after organs or tissues restore blood supply. Its main mechanisms include increased free radical generation, calcium overload, and the role of microvascular and leukocytes. The heart and brain are common damaged organs, manifested as changes in myocardial metabolism and ultrastructural changes, decreased cardiac function, etc. Prevention and control measures include removing free radicals, reducing calcium overload, improving metabolism and controlling reperfusion conditions, such as low sodium, low temperature, low pressure, etc. Understanding these mechanisms can help develop effective treatment options and alleviate ischemic injury.
Rumi: 10 dimensions of spiritual awakening. When you stop looking for yourself, you will find the entire universe because what you are looking for is also looking for you. Anything you do persevere every day can open a door to the depths of your spirit. In silence, I slipped into the secret realm, and I enjoyed everything to observe the magic around me, and didn't make any noise. Why do you like to crawl when you are born with wings? The soul has its own ears and can hear things that the mind cannot understand. Seek inward for the answer to everything, everything in the universe is in you. Lovers do not end up meeting somewhere, and there is no parting in this world. A wound is where light enters your heart.
Chronic heart failure is not just a problem of the speed of heart rate! It is caused by the decrease in myocardial contraction and diastolic function, which leads to insufficient cardiac output, which in turn causes congestion in the pulmonary circulation and congestion in the systemic circulation. From causes, inducement to compensation mechanisms, the pathophysiological processes of heart failure are complex and diverse. By controlling edema, reducing the heart's front and afterload, improving cardiac comfort function, and preventing and treating basic causes, we can effectively respond to this challenge. Only by understanding the mechanisms and clinical manifestations of heart failure and mastering prevention and treatment strategies can we better protect heart health.
Ischemia-reperfusion injury is a phenomenon that cellular function and metabolic disorders and structural damage will worsen after organs or tissues restore blood supply. Its main mechanisms include increased free radical generation, calcium overload, and the role of microvascular and leukocytes. The heart and brain are common damaged organs, manifested as changes in myocardial metabolism and ultrastructural changes, decreased cardiac function, etc. Prevention and control measures include removing free radicals, reducing calcium overload, improving metabolism and controlling reperfusion conditions, such as low sodium, low temperature, low pressure, etc. Understanding these mechanisms can help develop effective treatment options and alleviate ischemic injury.
carrier transport phenomenon
drift motion
Steady state
low electric field
Mobility m
Unit: cm^2/V*s
: Drift velocity is equal to mobility times electric field strength
Influencing factors
nonpolar semiconductor
Ionized impurity scattering
Proportional to
inversely proportional to
Phonon scattering mobility
:Semiconductor average longitudinal elastic constant
: Conductivity effective mass
: Band edge displacement caused by lattice expansion
Decreases with increase in conductance effective mass and temperature
Matheson resistivity
polar semiconductor
In-valley scattering
valley scattering
Related to mean free time and mean free distance
Conductivity/Resistivity
ne^2tao/m =neu
Determination experimental method: four-probe method
Correction factor
Measurement curve - the relationship between conductivity and impurity concentration. Generally, the more doped, the smaller the conductivity.
Hall effect
Carrier type (semiconductor type), carrier concentration, mobility
Hall coefficient
<0:n type
>0:p type
When a single carrier acts |RH|=rH/(nq)
rH is related to the average relaxation time and is determined by the concentration of carriers
Usually between 1 and 2
At very high magnetic fields, slightly less than 1
There is magnetoresistance effect under strong magnetic field
higher electric field
Does not consider transfer electron effects
medium electric field strength
Scattering Mechanism: Scattering of Acoustic Phonons The effective temperature of electrons in non-thermal equilibrium is greater than the lattice temperature
transition zone
Empirical formulas to maintain continuity
The electric field intensity is very high
Scattering mechanism: optical phonon scattering
The drift speed becomes less and less dependent on the electric field strength and gradually reaches saturation.
Si:Ep=0.063eV,vs~=1E7
GaAs:Ep=0.035eV,vs~=7E6
The saturation migration rate has nothing to do with the doping concentration and decreases with increasing temperature.
For polar semiconductors, transfer electron effects need to be considered
As electric field increases: inter-valley electron transfer (transfer from lower energy valley to higher energy valley) è effective mass increases è mobility decreases
ballistic transport phenomenon
Under high electric fields, the speed is higher than the steady-state speed for a short period of time, which becomes a speed overshoot.
impact ionization
Do collisions ionize impurities?
Ionization rate alpha
Influencing factors
Electric field strength
external accelerating electric field
equivalent threshold electric field
Thermal Scattering (Acoustic Phonon Scattering)
Optical phonon scattering
ionization scattering
deceleration effect
mobility
High field effective ionization threshold
?
bandgap
Large band gap -> large breakdown voltage -> large ionization rate
?
temperature
The higher the temperature, the smaller the ionization rate
calculate
The rate of change of carrier concentration at a certain fixed position with time
The rate of change of current density with spatial position at a certain moment
carrier lifetime
The recovery process from non-thermal equilibrium to thermal equilibrium
produce
Eigenexcitation
impurity ionization
When the carrier concentration is less than the value at thermal equilibrium
complex
Compound directly
band-to-band transition
More likely to occur in direct bandgap semiconductors
Direct bandgap semiconductors are more common among III-V compounds
indirect compound
surface level recombination
The bandgap energy level corresponds to
Defect energy level
way to release energy
emit photons
emit phonons
Auger compound
The reverse process of impact ionization
Recombination rate
Direct recombination (interband transition)
Composite coefficient Rec= Gth/ni^2
Recombination rate Re=Rec*n*p
Heat generation rate Gth
Net rate of change U=Re-Gth
n-type semiconductor
Small injection: U=Rec*Nd*delt p
Large injection: U=Rec*delt n*delt p
p-type semiconductor
Small injection: U=Rec*Na*delt n
Large injection: U=Rec*delt p*delt n
Bandgap energy level compliance (lattice defect)
Defect energy level Et
Defect concentration Nt
Single-level recombination: including electron capture and hole capture processes
Schottky-Reed-Hall statistics
U=. . . : Qualitative analysis
U is proportional to (np-ni^2)
When Et=Ei, U is the largest, so the defect with an energy level of about (Ec Ev)/2 is an effective recombination center.
Ei is the Fermi level of the intrinsic semiconductor which is slightly smaller than the intermediate energy level of the forbidden band.
n-type semiconductor
Small injection:
Big injection:
p-type semiconductor
Small injection:
Big injection:
Multi-level traps have qualitatively similar properties to single-level traps
carrier lifetime
Non-equilibrium carrier lifetime
Minority non-equilibrium carrier lifetime
n type
Compound directly
1/(Rec*Nd)
1/(Rec*delt n)
defect level recombination
p type
Compound directly
1/(Rec*Na)
1/(Rec*delt p)
defect level recombination
carrier generation lifetime
It is related to the carrier concentration: when n and p are small, the lifetime will be large.
Measurement method of minority carrier lifespan
Photoconductivity Effect PC
Photoelectromagnetic effectPEM
continuity equation
diffusion
Cause
Uneven spatial distribution of carrier concentration
Influencing factors
Thermal exercise--
scattering--
Fick's law
Thermal diffusivity D
Einstein relationship
Applicable conditions
non-degenerate semiconductor
Unit: cm^2/s
The flux of carrier concentration at a certain location along a certain direction is directly proportional to the magnitude and opposite to the concentration gradient at this location.
Diffusion length
With a fixed diffusion source as the boundary condition, the carrier concentration distribution is in exponential form, and the diffusion length is the characteristic length.
Thermionic emission
classical theory
The total electron current across the potential barrier is
A is called the effective Richardson constant
related to effective quality
Correction
quantum tunneling effect
For a potential barrier with finite width and finite height, the probability of electrons with energy less than the barrier crossing the barrier is not zero.
Tunneling probability Tt
Related to barrier height and barrier width
tunneling current
reflection
space charge effect
low field mobility mechanism
high field saturation mechanism
ballistic mechanism
Semiconductor device basic equations
electrostatic equation
Poisson's equation
Boundary conditions for the thin charge layer at the interface (Q is the surface charge density)
current density equation
continuity equation
Example
Decay of excess carriers over time
Decay of excess carriers with distance
Decay of excess carriers over time and distance
surface composite
, boundary conditions, minority carriers drifting to the surface recombine on the surface
S is the surface recombination speed