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2 votes

Cause non-linear relation between intensity and photo-current

As suggested I've used a ND filter instead of a polaroid to control the laser's intensity. This gave me the expected results, as shown in the figure below. As also said before: the beamsplitter ...
0 votes

Does carriers lifetime introduce any dispersion to a LED diode emitter?

Your provided information is incomplete. The chromatic dispersion coefficient (CDC) is a standard value for any manfactured fiber. The method to determine it is by using CD analyzers to measure the ...
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1 vote

What's actually happening on the level of individual particles when an atom in a solid is vibrating?

First things first At $T=0$, the ion cores (i.e. the nucleus of the atom + electrons in lower shells) form a perfect lattice (assuming no impurities). As Bloch Theorem shows, electrons (or better: ...
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1 vote

What's actually happening on the level of individual particles when an atom in a solid is vibrating?

Qualitatively: Atoms are quantum mechanical entities. They are described by a wavefunction which gives the probability in space time for the atom to exist at (x,y,z,t). An electron hitting a single ...
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0 votes

LED forward or reverse bias

An LED works like any standard diode. The current must overcome a small reverse electric field due to chemical effects. Some electrons in the N-doped side seep across to the P-doped side so as to ...
0 votes
Accepted

Is effective mass used in calculating kinetic energy of electron in semiconductor?

Effective mass is not the real mass of electrons. For a free electron we don't need to consider effective mass, here electron's real mass can easily describe things. But for electrons in solids (such ...
1 vote
Accepted

Photovoltaic cells vs. Second law of thermodynamics?

Let's say a big solar cell surrounds the sun. Now it's clear that the temperature of the radiation hitting the cell is 6000 degrees, temperature of the sun. Now photons create free electrons and free ...
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1 vote

Photovoltaic cells vs. Second law of thermodynamics?

I see two problems in your thought experiment: First, the equilibrium is not going to happen even if I go along with the (non-realistic) tacit assumption that the material will not undergo phase ...
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8 votes

Photovoltaic cells vs. Second law of thermodynamics?

The solar photosphere has a temperature of ~6000K. In theory, a body on Earth can be brought to equilibrium with that using a suitable optical system. Assuming that as a heat source, and assuming a ...
  • 10.9k
7 votes

Photovoltaic cells vs. Second law of thermodynamics?

The thought experiment assume equilibrium between the radiation and the photovoltaic cell, which is not the case in normal conditions: the cell is assumed to be collected to a sink that quickly ...
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0 votes

Can the base of a transistor not be an intrinsic?

To make a triode, you need a current channel and a way to control the potential in the channel. The carrier density in the channel has to be low to make it possible to control the potential. In in ...
  • 10.9k
1 vote

Can the base of a transistor not be an intrinsic?

I will try to keep this fairly simple. Note that, under all the simple stuff, the actual physics 'under the hood' may get quite complicated (but that is for undergraduate device physics courses). In a ...
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2 votes
Accepted

When a PN junction is in equilibrium, why is the electric field outside of the depletion region zero?

It's because there are free carriers. When you have free carriers, the electric field pushes them around until they cancel it. The depletion region can support an electric field because it doesn't ...
  • 10.9k
1 vote

Difference between photodiodes and avalanche photodiodes

The avalanche and standard diodes differs in their structure, mechanism, applications and responsitivity. Structure With respect to a standard photodiode, an additional layer is added in which ...
  • 647
1 vote

Difference between photodiodes and avalanche photodiodes

Both diodes rely on the generation of electrons and holes in the diode by photons. In the "normal" photodiode, the current is just the generation current, i.e., the current corresponding to ...
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1 vote

Semiconductors, diode in reverse bias

When the diode is not connected then the two currents flowing within the diode cancel out. Recombination current and thermal generation current. thermal generation current does not depend on the ...
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1 vote

Semiconductors, diode in reverse bias

This is one of the more confusing things in semiconductor physics. Indeed, undepleted p-type semiconductor is electrically neutral: the positive hole charge cancels the excess negative charge of the ...
  • 10.9k
1 vote

In the Esaki diode, how can one be 100% sure that there are tunnelling electrons with lower energy in comparison with the barrier's energy?

This is meant to compliment the answer from anna v. From this reference: https://ecstudiosystems.com/discover/textbooks/basic-electronics/diodes/tunnel-diodes/ This image contains all the proof. In ...
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0 votes

In the Esaki diode, how can one be 100% sure that there are tunnelling electrons with lower energy in comparison with the barrier's energy?

this is an extended comment : Solid state is modeled with quantum mechanics. Quantum mechanics is all about probability distributions, so it has to be accumulation of statistics. The quantum ...
  • 228k
0 votes

In the Esaki diode, how do physicists measure/estimate the velocity of a would-be-tunneling electron?

This is a long comment. At the level of diodes one is in the calculational range of quantum mechanics, the measuring the velocity of a single electron within the diode has no meaning. In quantum ...
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