All Questions
Tagged with electricity semiconductor-physics
61
questions
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59
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Can a DC voltage excite a pure semiconductor (or insulator) from the valence band to the conduction band?
I have a question I am sticking around and can't find a satisfying answer. Say I have an intrinsic semidonductor at zero Kelvin (no electrons in conduction band). I apply a DC voltage across it. Can ...
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1
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Isn't heating insulator enough for sufficient electrons to escape valence band and conduct electricity?
Diamond has about 5.5eV of energy gap, So If I heat diamond it will get atleast 1J energy which is enough to excite about 10^18 electrons, But Diamond still not conduct electricity, Why?
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1
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56
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Current Amplification in Common Base Transistor
How does a common base transistor amplify current if a small part of its emitter current gets divided into base current and the rest goes to collector current? If the input signal is applied to the ...
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1
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649
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Why is generation rate equal to recombination rate in extrinsic semicondcutor?
The mass action law states, that the product of electron concentration and hole concentration is equal to the square of the intrinsic carrier density. That applies to both intrinsic and extrinsic ...
1
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1
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215
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How can NO charge carriers exist in the depletion region?
I learned that no charge carriers exist in the depletion region of a PN junction due to the balance between the diffusion current and the drift current due to the electric field created by charged ...
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How do I calculate the standard uncertainty? Task on determination of energy gap width of semiconductors
I am creating a report for my physics class and all I have left to do is calculate the standard uncertainty for this formula.
$$ \ln \left( \frac{R_{T}}{R_{\infty}} \right) = \ln \left( R_{T} \right) -...
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49
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Where does the drift current in a pn juntion come from?
I know I know. There are around 4 similar questions on here, but they do not properly answer my question.
I'd like to know where the drift current in a pn juntion (no bias) comes from. From what ...
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25
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Do you get correct graph of transfer characteristic, if you take +ive Vds(constant) value instead of -ive. As mostly CNTFETs are p-chnl FET
I'm studying transfer characteristic curve of CNTFET to get value for mobility, S.S, etc. According to my basic background knowledge, NMOS curves lie in the 1st quadrant. While for PMOS they lie in ...
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2
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93
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Can we measure resistance of a diode using Ohm's law $V=IR$ for a specific value of voltage and current?
As a diode doesn't follow $V$ proportional to $I$, I was wondering if we can use Ohm's law to calculate its resistance for a specific set of voltage and current, as its resistance varies as per the ...
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31
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Will there by a voltage drop in the p-type in the diode?
Assume we have a pn diode, and we have forward bias so that we get electricity through the diode.
My question:
Will there be a voltage drop over the p type? (NOT the depletion laywer, but the rest of ...
- 199
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3
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987
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When an electron moves in the valence band, does it need energy?
I am wondering what actually happens when an electron moves in the valence band. As I understand an electron needs energy to free itself from an atom. Is it so that the electron gets energy to free ...
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720
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Why do electron holes move away from heat?
I'm currently learning about thermoelectric generators and I learned about the two p and n semiconductors. I understand how the n-type semiconductors works which is that when one side gets heated then ...
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4
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447
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PN junction: not sure to understand why reverse-biais lead to negligible current
My question is very highly related to Why doesn't current flow in reverse biased diode?
Basically, I would like to understand in more depth John Rennie answer. At $t=0$, I consider a PN junction ...
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729
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What is the relation between the short-circuit current and the band gap energy in solar cells?
For the VOC it is:
VOC = E_g - something,
where something is positive and depends on the Urbach energy. Otherwise it should be linear:
https://aip.scitation.org/doi/pdf/10.1063/1.49397
For the ISC I ...
2
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1
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78
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Why don’t illuminated series connected (photo-)diodes bias each other?
When you connect, let's say, three photodiodes or solar cells, with a load, and you measure the voltage across the middle photodiode. Will the voltage change if
the adjacent cells are in the dark
if ...
2
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1
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945
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Why is the diffusion length defined for minority charge carriers only?
As far as I could infer from the solar cell literature, when talk is about the "diffusion length", only the minority carriers are concerned.
Is there a diffusion length defined for majority ...
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1
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885
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Why are we even interested in solar cells under bias voltage?
I couldn't find any answer on this super basic question.
Some people on the internet say that you would not put a solar cell in an array under bias, others say that they bias themselves, but I don't ...
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Understanding a charged isolator
If an isolator gets charged (e.g. by rubbing it to an other isolator), it can get charged. If it is negatively charged, I would expect the additional electrons to be in the conduction band, so that ...
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1
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165
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What are the different driving forces behind a solar cell and how is a voltage created?
I have a hard time understanding the I-V curve of a solar cell. I dont understand how in an short circuit a current can happen although there is no voltage? Isn't voltage the requirement for a current,...
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2k
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How to know a semiconductor is p type or n type from hall effect calculations? [closed]
Using the hall effect calculations how can we determine a semiconductor is p type or n type
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1
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284
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Is there a potential difference across the bulb after current passed through a diode?
I understand that voltage can exist without current so what I want to ask is will there be a potential difference across the bulb(situated after the diode) when a batteries supplied energy through a ...
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1
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265
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Why do diodes block current in a single direction?
It seems like all the explanations for diode mechanics simply state that if N-type semiconductor is connected to V+ of the battery, the depletion region grows so current cannot pass.
It seems, ...
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35
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Is activation voltage the sum of voltage required to collapse depletion layer and band gap energy?
Is the energy released when an electron moves from the valence to conductance band states the activation voltage or is activation voltage the energy required for electrons to overcome the depletion ...
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74
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How do electrons exit LEDs? Aren't they in the valence energy state?
If a conducting electron reduces to the valence band in an LED, where does it get the energy to go back to the conductance band upon leaving the diode so current can flow?
I'm confused as to how ...
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237
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Electric fields and electric potentials in semiconductors
The zener diode is heavilier doped than a normal diode , that is why its depletion region is smaller than the delpetion region of a normal diode and that is why the electric field is very strong.Zener ...
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76
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Zener diode electric field working principle
Well I recently saw a video from khan academy about zener diodes.This video was suggested by another member of Stack Exchange Physics who I thank him very much . But I didnt understand some things:...
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At what pressure do semiconductors break down? [closed]
So let's say you were going to send some electronics to the bottom of the ocean, 3-5km down. This would be about $5km*1000kg=5Mkgf/m^{2}$. So at what pressure do circuit boards, transistors, etc stop ...
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1k
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How can depletion region be formed at the center?
Let's consider an electron at the junction in the n-type region. As it moves into the p-type we say it leaves behind a positive ion and hence in this way electrons at the junction in the n-type create ...
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2
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1
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983
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Confusion regarding Hall effect in semiconductors
In many places, it's mentioned that in hall effect, the holes move under the influence of magnetic field in the direction as shown in the figure. In this figure itself, the bound electrons move in the ...
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Hall-Voltage behaviour with increasing temperature
I have a question relating to this diagram:
It shows the relationship between Temperature and Hall-Voltage of a P-doped Germanium Plate. The electron density n is constant from 10°C to 50°C, that's ...
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2
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Why in a conductor increase in temperature makes the atoms vibrate but in a semiconductor the kinetic energy of the free electrons is increased?
When temperature is increased in case of a semiconductor the free electron gets more energy to cross the energy gap to the conduction band from the valence band.so now more electrons can go easily to ...
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3
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249
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Doubt in working of p-type semiconductors
Correct me if I'm wrong, but as far as I know, in p-type semiconductors, first the excitation of an electron takes place from the valence band to the conduction band due to thermal energy, then this ...
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74
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Point resistance
The resistance of a given object is expressed through:
$$R=\rho\frac{l}{A}$$
I'm wondering if there is any quantity like resistance at a specific point. For example, $R$ for a copper wire with l=...
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2
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952
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Does an electron physically flow? [duplicate]
In a DC current in a conductive wire, is it more accurate to think of one electron wiggling its way through a sea of electrons... or to think of one electron bumping into another, which bumps into ...
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2
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3k
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Construction of Peltier tiles
I'm learning about the construction of Peltier tiles from Wikpedia. However, some of the statements in the article are not at all clear.
Here's the extract:
Two unique semiconductors, one n-type ...
user139621
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Differences in conductivity as temp rises for intrinsic vs extrinsic semiconductrs
For a doped semiconductor, near the end of the extrinsic temp region due to heightened effects of lattice scattering conductivity goes down "temporarily" (temperature wise).
What happens to the ...
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3
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Are thermistors and filament bulbs ohmic?
Conductors are ohmic if they have a constant resistance given that the physical conditions, such as temperature, are constant.
A filament bulb and thermistor are considered to be non-ohmic because ...
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2
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3k
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Why does current have to flow in the same direction?
If current is just the movement of charged particles, why do the all have to move in the same direction?
For example, if you reverse-bias a diode (connect the positive terminal to the n-type side ...
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1
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How can I create an ohmic contact with selenium?
I would like to be able to measure the electrical resistance of selenium past its melting point, but to do this I need to create an Ohmic contact between the selenium and my multi-meter. What metals ...
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37
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How am I obtaining silicon with resistivity proportional to the number of conduction electrons?
The resistivity of silicon is given by
$$\large\rho=\rho_0e^{\Large{{\frac{E_g}{2k_BT}}}}$$
and the number of conduction electrons in a semiconductor conduction band is
$$\large n_{\text{...
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1
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180
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If we inject charge carriers into insulators, will they become conductors?
Since there're also valance band and empty band in insulators, if we introduce electrons in empty band or holes in valance band, will it conduct electric current like semiconductors?
For example, we ...
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2
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176
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Van der pauw method for an isolated hole
Van der pauw method is a way to measure the resistivity of a material with arbitrary shape while it meets some specifications ( being homogeneous and ...).
One of the conditions is that the sample ...
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215
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Simulate Band Bending and Band Alignment in Semiconductors
Are there softwares (simple ones preferred) where we can simulate the band alignments and band bending of a p-n junction, where we can vary properties of the junction materials such as carrier ...
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1
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496
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Quasi-fermi levels in a solar cell?
I was wondering, if my fermi levels splits up due to n and p type doping into two fermi levels, one for the p type one for the n type, and now due to light radiation my fermi levels split up into 2 ...
user85397
3
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1
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3k
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Do batteries provide electrons
In chemistry, the reaction at negative electrode produces electrons,which flow to the positive electrode through the circuit. But then, if circuit has a conductor, then wouldn't it also release ...
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1
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183
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How does the solar cell work?
I know that a solar cell consists of a transistor (NP). First step it creates a barrier between the n type and the p type junction. Then the sunlight (i.e, the photons) supply energy to the electrons ...
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4
answers
16k
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How is current produced in semiconductors or metals?
I think current is the movement of electrons through the wire or semiconductor, thus when I press the switch of the light bulb the electrons go from positive part to tungsten and light is produced. ...
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1
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1k
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Question on Shockley's equation for FETs
I'm currently studying FETs (Field Effect Transistors) in Navy school. What I know so far is that in FETs, $V_{gs}$ is reversed biased, creating a depletion zone. What this means in plain English is ...
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1
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715
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How to check the ohmic contact to the film?
I have a thin semiconductor film deposited on an isolating substrate. I would like to check different metals to find out do they form the ohmic contact or Schottky barrier.
What is the best way to do ...
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0
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How does Passivation in Mercury-arc-valve cause "diode" behavior
Does passivation of lead anodes cause them to become semiconductors?
Or even become diodes (eg. a p-n passage)?
How does this work on an atomar level?
This question has been risen by trying to ...
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