Newest questions tagged semiconductor-physics - Physics Stack Exchange most recent 30 from physics.stackexchange.com 2019-07-17T20:44:42Z https://physics.stackexchange.com/feeds/tag?tagnames=semiconductor-physics&sort=newest http://www.creativecommons.org/licenses/by-sa/3.0/rdf https://physics.stackexchange.com/q/492132 0 applied voltage on n-typed semiconductor changes its carrier lifetime dor00012 https://physics.stackexchange.com/users/190284 2019-07-17T14:11:52Z 2019-07-17T16:54:54Z <p>An apparatus was constructed in the lab to measure charge carrier lifetime.</p> <ul> <li>An LED illuminates an n-typed germanium semi-conductor with a square function with a constant frequency (the period of the illumination is such that the charged carrier density reaches saturation).</li> <li>A constant current flows through the semiconductor so that the voltage on it is measured time dependent using a scope.</li> </ul> <p><a href="https://i.stack.imgur.com/BvqmA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BvqmA.png" alt="voltage on semiconductor vs. time"></a></p> <p>Using the described apparatus, an exponential decay of the voltage is measured each time the LED is turned off, and its life time is measured.</p> <p>When the current that flows through the semiconductor is increased, the lifetime is changed (the negative current part can be ignored for this question)</p> <p><a href="https://i.stack.imgur.com/J08QP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/J08QP.png" alt="life time vs. current"></a></p> <p>My question is how can one explain this phenomenon? I might be able to describe the decrease in life time, by knowing that the temperature increases with current, hence electron density increases which lowers the lifetime (more electrons for the holes to perform recombination).</p> <p>But the part i really can't understand is the increase in lifetime at the low current values. Any insight will be valuable, thank you. </p> <p>*EDIT - it may be important to mention that the experiment was reproduced on 3 different samples.</p> https://physics.stackexchange.com/q/492103 0 Hall coefficient '$R_H$' for intrinsic semiconductor Suresh https://physics.stackexchange.com/users/182365 2019-07-17T11:10:22Z 2019-07-17T11:10:22Z <blockquote> <p>The Hall coefficient of an intrinsic semiconductor is:<br> A) Positive<br> B) Negative<br> C) Zero<br> D) Infinite<br> ? </p> </blockquote> <p>What will be the best answer for this question?<br> According to me<br> It should be very large or <strong>D) Infinite</strong> as<br> <span class="math-container">$$R_H = \frac{1}{q \, n}$$</span> <span class="math-container">$$\text{where, } q = \text{ charge , and } n = \text{ total no. of carriers}$$</span> and in intrinsic semiconductors as <span class="math-container">$n$</span> is very small,<br> <span class="math-container">$\therefore \, R_H$</span> is very large </p> <p>So, am I right or there is more reasonable answer for any other option?<br> Any hints/suggestion or help please ...</p> https://physics.stackexchange.com/q/491693 0 MOS Capacitance variation with Voltage [on hold] Muralidhar M https://physics.stackexchange.com/users/236896 2019-07-15T07:39:42Z 2019-07-15T08:10:49Z <p>Can anyone indicate me about the details of MOS <strong>static capacitance</strong> variation with applied Vgb (gate to substrate voltage)? what I found in the literature is (afraid not) dynamic capacitance in various regions of operation...using superimposed ac voltage on the applied DC bias.</p> https://physics.stackexchange.com/q/491419 0 How can one determine the key characteristics of a solar cell from the I-V curve? Pearson73 https://physics.stackexchange.com/users/236788 2019-07-13T15:59:21Z 2019-07-13T17:40:57Z <p>I have recently measured the IV characteristics of several Si solar cell samples and am now attempting to extract the series resistance <span class="math-container">$R_S$</span>; parallel resistance <span class="math-container">$R_P$</span>; open circuit voltage <span class="math-container">$V_{OC}$</span>; short circuit current <span class="math-container">$I_{SC}$</span> and fill factor. </p> <p>From what I have read, I understand that <span class="math-container">$V_{OC}$</span> is the voltage across the cell, for zero current flow and <span class="math-container">$I_{SC}$</span> the current flowing for zero voltage across the cell. Fill factor is the ratio of IV at maximum power production to the product of <span class="math-container">$I_{SC}$</span> and <span class="math-container">$V_{OC}$</span>. I am, however, struggling to determine these values from my data (one example of the plotted data is shown below, please note that the orders of magnitude on the axis are off); all other IV graphs I have seen, have had a very different appearance, starting from a plateau at <span class="math-container">$I_{SC}$</span>, before decaying down into <span class="math-container">$V_{OC}$</span>, allowing both to be easily determined, as well as the fill factor.</p> <p><a href="https://i.stack.imgur.com/3DO48.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3DO48.jpg" alt="I-V curve for varying levels of illumination"></a></p> <p>I also understand that <span class="math-container">$R_S$</span> is to be found from the ln(I)-V curve, by finding the variation between the high-current section of the graph and the best fit of linear mid-current section and then plotting this voltage deviation against I, whereupon the gradient yields <span class="math-container">$R_S$</span> (see below graph).</p> <p><a href="https://i.stack.imgur.com/EKt7L.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EKt7L.jpg" alt="Construction line to determine voltage difference between linear continuation and actual data."></a></p> <p><span class="math-container">$R_P$</span> is to be found by taking the inverse gradient of the linear portion of the I-V plot approaching zero voltage.</p> <p>My question, so to speak, is whether my above stated understandings are correct and also how to extract the fill factor,<span class="math-container">$V{OC}$</span> and <span class="math-container">$I{SC}$</span> from my graph.</p> https://physics.stackexchange.com/q/490448 1 How is quantum physics translated into the world of electronics? [on hold] mskayyali https://physics.stackexchange.com/users/236375 2019-07-08T13:58:38Z 2019-07-08T15:36:37Z <p>I remember watching a documentary about early works in quantum physics and how it was essential to the microelectronics revolution and the invention of the transistor. What part exactly helped? Is there a source on technical aspects that lead to such development? </p> https://physics.stackexchange.com/q/490187 1 Does semiconductor laser need stimulating photon to produce coherent light? Codelearner777 https://physics.stackexchange.com/users/119217 2019-07-07T02:15:48Z 2019-07-07T03:29:53Z <p>In regular laser, we need:</p> <ol> <li>stimulating photon => this makes the output light coherent</li> <li>ways to make inversion population</li> <li>resonant cavity</li> </ol> <p>in the pictures about semiconductor laser, I do not see any incoming photon. I checked it in the book Solid state devices by Banerjee and in the internet. Does semiconductor laser need stimulating photon to produce coherent light?</p> <p>if it does, what is used to produce that stimulating photon?</p> <p>if it does not, how is a coherent light output produced?</p> https://physics.stackexchange.com/q/490000 0 Fano factor measurements Rizalina Mingazheva https://physics.stackexchange.com/users/220763 2019-07-05T22:00:07Z 2019-07-05T22:00:07Z <p>I am looking for information on the measurements of the Fano factor, in particular in germanium. Does anyone know accessible papers?</p> https://physics.stackexchange.com/q/488347 0 What happens when electron keeps hitting on a metal plate Dil Azat https://physics.stackexchange.com/users/220663 2019-06-26T17:22:55Z 2019-06-26T17:22:55Z <p>In SEM, in order to 'focus' the electron beam, an aperture is used (which usually is metal); what happens to the metal after so many electron hits the metal constantly? </p> <p>since metals are usually are saturated, and its in vacuum; its highly unlikely no chemical reaction happens, but does it make any kind of change to the metal? </p> <p>based on my assumption, if there is no chemical reaction, there should be no chemical change or physical change, but I hope someone could shed a light on this for me. </p> <p>Thanks a million!</p> https://physics.stackexchange.com/q/487998 0 Fermi level in metals and semicoductors Rai Arman https://physics.stackexchange.com/users/235409 2019-06-25T08:23:57Z 2019-06-25T13:29:43Z <p>As we read about Fermi energy, it is the energy of the highest occupied electrons. But if we look at the energy level diagram of semiconductor the Fermi level is situated somewhere between the valence band and the conduction band. The probability of the occupancy of the Fermi energy level is zero. If there enter some electrons in the conduction band due to thermal excitation conduction happens. My question is that how does the energy of the electrons whose energy is above the Fermi level, against the definition of the Fermi energy, are not called to be present at the Fermi energy level? </p> https://physics.stackexchange.com/q/487360 1 The n-type dopant elements on silicon Payman Rajai https://physics.stackexchange.com/users/169986 2019-06-21T20:29:48Z 2019-06-22T05:55:02Z <p>The n-type dopant elements on silicon are phosphorus, arsenic, and antimony from the group V elements. My question is that what is the difference between doping P, As, or Sb? How do we decide to dope whether P, As, or Sb?</p> <p>Payman</p> https://physics.stackexchange.com/q/487169 0 Temperature influence on Hall Effect for semiconductor Tandeitnik https://physics.stackexchange.com/users/173965 2019-06-20T17:59:30Z 2019-06-20T17:59:30Z <p>Currently, I'm taking a course in modern physics experiments and last week I was asked to study the hall effect in a semiconductor. One of the experiments was with a germanium chip where a steady current of <span class="math-container">$20\,mA$</span> was flowing and with a uniform magnetic field going through it, standard hall effect setup. The variable that we controlled was the temperature of the chip, we started at room temperature (300 K) and heated it up to 420 K, meanwhile reading off the hall potential <span class="math-container">$V_{hall}$</span>. Here is the result:</p> <p><a href="https://i.stack.imgur.com/fD1p1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fD1p1.png" alt="enter image description here"></a></p> <p><span class="math-container">$V_{hall}$</span> initially increased with the temperature increase but suddenly, somewhere between 380-400 K, it started to drop. We learned that <span class="math-container">$V_{hall}$</span> should obey this equation:</p> <p><span class="math-container">$V_{Hall} = \frac{IH}{enw}$</span></p> <p>Where I is the current, H is the magnetic field, e is the elementary charge, <strong>n is the density of the charge carriers</strong> and w is the width of the chip. So I did some research and found this:</p> <blockquote> <p>As you know hall coefficient depends on the carrier density and type of carriers,So in metals electrons scattering increases with phonons with increase in temperature so the free electron density changes.</p> </blockquote> <p>Raising the temperature should raise the number of phonons that will scatter the charge carriers and thus <span class="math-container">$n$</span> will drop, raising the value of <span class="math-container">$V_{hall}$</span>. OK, my data supports this between 300-400K. My question is: why it started to drop at higher temperatures? I researched for it and couldn't find the answer.</p> https://physics.stackexchange.com/q/487147 1 How does one obtain a semiconductor's absorption coefficient from first principles? Malcolm Regan https://physics.stackexchange.com/users/130852 2019-06-20T15:21:31Z 2019-06-20T15:41:07Z <p>Is the absorption coefficient of a semiconducting material at a given wavelength obtainable from the material's band structure? If so, how? Are there any pedagogical papers you could recommend to help me understand this?</p> https://physics.stackexchange.com/q/485727 1 Conceptual question regarding transistor biasing Nirmal Padwal https://physics.stackexchange.com/users/232258 2019-06-12T18:32:05Z 2019-06-12T19:26:07Z <p>I know that in a transistor, the base-emitter (B-E) junction has to be forward biased while collector-base (C-B) junction needs to be in reverse bias.</p> <p>Question: What would happen if we alter this biasing?</p> <p><strong>Case 1:</strong> Both B-E and C-B junctions are reverse biased.</p> <p>Guess: Nothing will happen as electrons are being pulled away from the base region leading to no flow of current.</p> <p><strong>Case 2:</strong> C-B junction is forward biased and B-E junction is reverse biased</p> <p>Guess: Transistor can be operated in normal fashion. But I know that collector is purposefully designed to be larger for heat dissipation. In our case, as emitter (which is not as large as collector) serves the purpose of a collector. It will cause heating in our circuit which can damage the transistor.</p> <p><strong>Case 3:</strong> Both B-E and C-B junctions are forward biased.</p> <p>Guess: For this one, I suppose one out of two things should happen (I am not sure what). </p> <p>Possibility 1: As both junctions are forward biased, electrons accumulate at the thinly occupied thinly doped base region. This causes overheating thus damaging the transistor.</p> <p>Possibility 2: As both junctions are forward biased, electrons accumulate at the thinly occupied thinly doped base region. This constitutes to rise in base current. Thus transistor conducts like two independent separate diodes.</p> <p>Are these above guesses right or wrong? Detailed explanation would be helpful</p> https://physics.stackexchange.com/q/484070 0 Half wave rectifier confusion F.sharmin https://physics.stackexchange.com/users/217261 2019-06-03T14:55:56Z 2019-06-03T16:15:06Z <p>I am searching for a good book or link or video that might give some fresh idea about half wave rectifier properties I mean in my book prescribe by my university that has introduced some of the basic formulas Like I(rms)=i(m)/2 or I(avg)=I/pai value. But i really want to know about how these formulas originated. I have searched through the internet but they almost have the same kinda thing. I have surfed through the Art of electronics but I think its a little advanced for me and they dont have what im searching for. anyone please share any source or article or anything that would be helpful for me.</p> https://physics.stackexchange.com/q/484032 0 Is activation voltage the sum of voltage required to collapse depletion layer and band gap energy? Eloise https://physics.stackexchange.com/users/233544 2019-06-03T11:20:36Z 2019-06-03T11:20:36Z <p>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 layer?</p> https://physics.stackexchange.com/q/484024 0 How do electrons exit LEDs? Aren't they in the valence energy state? Eloise https://physics.stackexchange.com/users/233544 2019-06-03T10:30:11Z 2019-06-03T10:48:41Z <p>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 current can flow completely through an LED if all electrons are reduced to the valence electron state, meaning they are not conducting electricity. Do the electrons return back to the conductance band energy state?</p> https://physics.stackexchange.com/q/483075 0 Why n and p are not additive in law of mass action? or Why is the sum of electron concentration and hole concentration is not constant? Indrasish Chakraborty https://physics.stackexchange.com/users/233118 2019-05-29T06:20:35Z 2019-05-29T15:37:25Z <p>I was asked this question during a viva examination. I tried to give answer through mathematical derivation but I was told to give the answer from intuition.</p> <p>So why is <span class="math-container">$n_0 p_0 = n_i^2$</span>, and not <span class="math-container">$n_0 + p_0 = \text{(some constant)}$</span></p> <p>Why is <span class="math-container">$n_0 + p_0$</span> not constant ?</p> https://physics.stackexchange.com/q/482716 0 Simulation of QW gain Dj1312 https://physics.stackexchange.com/users/133102 2019-05-27T12:53:39Z 2019-05-27T12:53:39Z <p>For a student project, I need to compute and plot the gain of a semiconductor quantum-well.</p> <p>In my case, I am interested to reproduce the results from Schwartz et al. (<em><a href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/6485/648506/Investigation-and-comparison-of-optical-gain-spectra-of-AlInGaN-laser/10.1117/12.705867.short?SSO=1" rel="nofollow noreferrer">Investigation and comparison of optical gain spectra of (Al,In)GaN laser diodes emitting in the 375 nm to 470 nm spectral range</a></em>). Unfortunately, everytime I try to compute using given formulas, I obtain false result...</p> <p>So, I am here today to ask if someone can help me to find if there is errors in this article or if someone had already make such a simulation. And in this last case, if a script is available !</p> <p>Thanks in advance, Dj1312.</p> https://physics.stackexchange.com/q/482539 0 Electrical properties of the Wannier exciton Paris https://physics.stackexchange.com/users/195517 2019-05-26T13:52:36Z 2019-05-26T13:52:36Z <p>We know that excitons are charge neutral and doesn't show any electrical properties, but is it the same for Wannier exciton too? For example, if a Wannier exciton placed in the electric field, can it behave like a charged particle?</p> https://physics.stackexchange.com/q/482413 0 Why there is no reabsorption in LED crystals? Vladyslav Karnaushenko https://physics.stackexchange.com/users/232951 2019-05-25T21:48:51Z 2019-05-26T08:41:03Z <p>Can you explain to me please, why there is no reabsorption in crystals which are used as LEDs? Because the energy of emitted light is the same as the band gap of the semiconductor - it should be absorbed. Why is it not?</p> <p>Thanks in advance</p> https://physics.stackexchange.com/q/482257 0 Question about the purpose of a transistor [closed] E.Berk https://physics.stackexchange.com/users/208374 2019-05-25T09:14:55Z 2019-05-25T10:22:56Z <p>I've been studying about diodes and transistors and something made me wonder about the purpose of transistors. </p> <p>In the examples we were talking about increasing current by using two batteries with a transistor and I understood how the transistor transfers the current from one side to another while increasing it with another battery connected to both sides(probably I still have gaps with my knowledge).</p> <p>But the problem is: I didn't understand why we need transistor to increase current, can't we do the same thing by just connecting two batteries together or just using a transformator to increase voltage to get more current or just simply using a bigger battery? </p> <p>Maybe I'm thinking so straight logic now but examples did not look satisfying to me to understand the usefulness of transistors as I know how widely they are used especially in computer science (which is I'm interested and planing to study in university.) so I would like to hear better examples with explanations.</p> https://physics.stackexchange.com/q/481573 0 Half-wave rectifier output graph Sourav Bhattacharya https://physics.stackexchange.com/users/232642 2019-05-22T03:29:36Z 2019-05-22T03:42:20Z <p>I want to know what will be the output V-t graph when you connect a half-wave rectifier to a battery using an inverter instead of a traditional AC source? Because when I tried it, the output graph was inverted, not what I was expecting (I was expecting the graph to be similar to the graph when we connect it to a traditional AC source). Why this happens? Was I doing something wrong?</p> https://physics.stackexchange.com/q/481262 1 Semiconductor and temperature dependence Grace mars Mars https://physics.stackexchange.com/users/232391 2019-05-20T14:11:53Z 2019-05-20T16:23:34Z <p>Does the conductivity of both intrinsic and extrinsic semiconductor increases with temperature or is it that conductivity of extrinsic semiconductor decreases with temperature just like a conductor ?</p> https://physics.stackexchange.com/q/480808 0 Electronics and junctions Marium Mansoor https://physics.stackexchange.com/users/232244 2019-05-18T08:55:31Z 2019-05-18T09:08:27Z <p>In a p-n junction, is it only the electrons that move from the n-type part to the p-type part in order to create a depletion region or is it the movement of both electrons and holes from the n-type and the p-type respectively? If it is so, then the whole idea of a depletion region seems flawed, considering how there is a net movement of electrons and holes both. Can someone explain? </p> https://physics.stackexchange.com/q/480056 1 How insulators and conductors were discovered? user230720 https://physics.stackexchange.com/users/0 2019-05-14T17:10:53Z 2019-05-16T05:40:42Z <p>I know Stephen gray has discovered insulator and conductor. But I want to know that how did he know which one is conductor and which one is insulator ? Please tell me the details how had he done that above thing (that is conductor and insulator)</p> https://physics.stackexchange.com/q/479459 1 Why does the base-emitter voltage in NPN transistor become constant pjHart1000 https://physics.stackexchange.com/users/225116 2019-05-11T23:05:49Z 2019-05-12T00:03:05Z <p><a href="https://i.stack.imgur.com/HbVDI.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HbVDI.jpg" alt="enter image description here"></a></p> <p>The setup above shows the experiment that I have been working with. During the experiment, the current <span class="math-container">$i_c$</span> and the voltage <span class="math-container">$V_{be}$</span> were measured for increasing <span class="math-container">$V_{in}$</span>. At some point, the current through the collector will be constant, due to the barrier in the forward-biased base-emitter region being lowered as much as possible by <span class="math-container">$V_{in}$</span>, meaning that its maximum value follows Ohm’s law.</p> <p>As we further increase <span class="math-container">$V_{in}$</span>, we will find that <span class="math-container">$V_{be}$</span> will go towards a constant value. Why is that? Shouldn’t it increase too? I have great trouble understanding this last part. </p> <p>I will appreciate any help! </p> https://physics.stackexchange.com/q/479159 0 Resource recommendation for spintronics Luqman Saleem https://physics.stackexchange.com/users/140141 2019-05-10T12:58:29Z 2019-05-10T13:50:52Z <p>What are some good beginner level books to understand <a href="https://en.wikipedia.org/wiki/Spintronics" rel="nofollow noreferrer">spintronics</a>. I am looking for some sources in which basic mathematics of spintronics is properly explained.</p> https://physics.stackexchange.com/q/478755 0 Which statistical distribution could be assumed for the mobility of Silicon substrate material? user32038 https://physics.stackexchange.com/users/231472 2019-05-08T14:37:15Z 2019-05-09T06:53:04Z <p>Mobility is a key parameter for Hall elements or in transistor models. If we measure the mobility on Si wafers, then we can expect some variation from die to die or sample to sample. Which statistical distribution should be assumed for this? A normal distribution is <strong>not</strong> a good model because it ranges from -infinite to infinite, but mobility has to be a <strong>positive</strong> number of course. <br> It would be good to find references about this topic, or even measurement results from semiconductor fabs. We are not only interested for a good model fit in the body of the data, but also in the distribution <strong>tails</strong>, because just these extreme samples can ruin a product fabricated on such wafers (not necessarily Silicon). Or are there built-in models with suited mobility distributions in TCAD programs?<br><br> Unfortunately I have no raw data, only a Gaussian fit for a MOS transistor model, and often this fit arise from quite noisy data, and also often the mobility model parameter is not fit for physical meaning but just for fitting things not modeled by other parameters.</p> https://physics.stackexchange.com/q/478465 1 Is this photodiode-based "energy harvester using the coldness of outer space" just based on established thermoelectric effects? uhoh https://physics.stackexchange.com/users/83380 2019-05-07T06:45:44Z 2019-05-07T11:24:16Z <p>I've read through the explanation and can not understand what they are saying in terms of the underlying physics. My hunch is that this is a demonstration of a well established thermoelectric effect made to look more profound through obscuration, but I could be wrong.</p> <p><strong>Question:</strong> Is this photodiode-based "energy harvester using the coldness of outer space" just based on established thermoelectric effects?</p> <p>Wikipedia's article on the <a href="https://en.wikipedia.org/wiki/Thermoelectric_effect" rel="nofollow noreferrer">Thermoelectric Effect</a> says:</p> <blockquote> <p>The term "thermoelectric effect" encompasses three separately identified effects: the <strong>Seebeck effect, Peltier effect, and Thomson effect</strong>.</p> </blockquote> <p>The paper in question appears as an <strong>Applied Physics Letter:</strong> <a href="https://aip.scitation.org/doi/10.1063/1.5089783" rel="nofollow noreferrer">Experimental demonstration of energy harvesting from the sky using the negative illumination effect of a semiconductor photodiode</a> and the abstract reads:</p> <blockquote> <p><strong>We experimentally demonstrate electric power generation from the coldness of the universe directly, using the negative illumination effect when an infrared semiconductor diode faces the sky.</strong> Our theoretical model, accounting for the experimental results, indicates that the performance of such a power generation scheme is strongly influenced by the degree of matching between the responsivity spectrum and the atmospheric transparency window, as well as the quantum efficiency of the diode. A Shockley-Queisser analysis of an ideal optimized diode, taking into consideration the realistic transmissivity spectrum of the atmosphere, indicates the theoretical maximum power density of 3.99 W/m2 with the diode temperature at 293 K. The results here point to a pathway towards night-time power generation.</p> </blockquote> <p>For reference, Phys.org's <a href="https://phys.org/news/2019-05-experimental-device-electricity-coldness-universe.html" rel="nofollow noreferrer">Experimental device generates electricity from the coldness of the universe</a> says:</p> <blockquote> <p>An international team of scientists has demonstrated for the first time that it is possible to generate a measurable amount of electricity in a diode directly from the coldness of the universe. The infrared semiconductor device faces the sky and uses the temperature difference between Earth and space to produce the electricity.</p> </blockquote> <p>Spacecraft and planetary rovers use the "coldness of the universe" all the time. Their <a href="https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator" rel="nofollow noreferrer">Radioisotope Thermoelectric Generators</a> pass heat through a large array of thermocouple junctions with the cold side facing the cold of space. Is this new result any different than this?</p> https://physics.stackexchange.com/q/478328 0 What is the definition of a bipolaron and a dipolaron? Fraenzine https://physics.stackexchange.com/users/231271 2019-05-06T15:24:11Z 2019-05-06T15:24:11Z <p>I wondered about the exact definition of a bipolaron? In particular, if I have an oxygen vacancy in a metal oxide and the 2 excess electrons (when forming a neutral oxygen vacancy) localise on the 2 surrounding metal atoms, is this a bipolaron? And does the term "dipolaron", for having two electrons (holes) localised at the same (metal) centre, exist?</p>