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This (upvoted and answer-accepted) question was closed for lack of clarity. I'm trying to understand why and how it should have been written. Band bending under electric field in heterojunctions

At the time it was closed I had already posted an answer that is now accepted. I was able to do so because the question is a very clearly asked straightforward question about semiconductor device physics that anyone with a basic understanding of the material could answer. Despite having a sufficient understanding of the question to answer it, I'm not sure how I would edit the question to make it more clear without adding information that someone who needs to ask such a basic question wouldn't know, or adding elementary background information that someone able to answer the question wouldn't need.

The comments on the question give little insight. There are comments that do many things except give this clarity, including:

  • imposing their own standards on the question that are not supported by stackexchange rules (requiring captions for figures)
  • are complains about missing context that are misguided as the body of the question directly refers to the figure and gives that context

There are specific requests for information that may be construed as a request for clarity, but these are likewise misguided as they are asking questions that someone familiar enough with the material to answer the question wouldn't need to ask, as they are asking about fundamentals. Specifically:

  • "where is the insulator?" This is plainly obvious to someone familiar with band diagrams and shouldn't need to be explained in a question like this. (It is between the two metal regions)
  • "Are these identical metals?" Irrelevant to the question so it doesn't need to be explained in the question.
  • "What is ϕ?" Perhaps this could have been explained in the question, but like the half dozen or so other symbols used in the question it is a standard symbol used in semiconductor physics that doesn't need to be explained in a question. (For those unfamiliar, it is barrier height)

The above need not be explained in the question because it is fundamental information that someone familiar with the topic will already know. Nobody who needs the above explained would be able to answer the question. There is no physics stackexchange rule that one must write a textbook establishing the framework under which the question is asked. Many of the questions asked here are on advanced topics that not everyone understands. That does not mean the question lacks clarity.

Given the above, the only votes that I can explain are plainly based on a faulty understanding of this site and the material of the question. These are not reasons to vote to close a question.

Can anyone provide insight into how this question could be improved?

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  • $\begingroup$ I didn't vote to close. Seems like potentially an answerable question, but I disagree that it is "very clear[]" and "straightforward." BTW, you also have a repeated typo in your answer ("delpetion [sic]"). $\endgroup$ Commented Jan 10 at 23:29
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    $\begingroup$ I would also like to know how you became the arbiter of what is and what is not a "standard symbol" in semiconductor physics. If the question and answer are going to be useful to anyone other than yourself or others familiar with all the so-called "standard symbols" then the symbols should be explained. $\endgroup$ Commented Jan 10 at 23:39
  • $\begingroup$ @hft I'm not the arbiter of standard symbols, I'm just telling you how it is. If you are not familiar with phi as the symbol for barrier height it is exceedingly unlikely you will know the answer to this question. But also, phi is a distraction. It has no bearing on the answer. Thanks for pointing out the typo. I dont seem to get spellcheck on mobile and tiny on screen keyboards are a poor substitute for a real one. $\endgroup$ Commented Jan 11 at 1:22
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    $\begingroup$ I guess my point is that just because the question is clear to you does not mean it is clear to all the readers of this website. The best questions and answers are useful to the physics community at large, rather than specialists. If the question was unclear to at least three reviewers, it seems like it would be unclear to most readers and then not as useful as a more clear question. $\endgroup$ Commented Jan 11 at 1:47
  • $\begingroup$ It is probably not helpful to critique what some website users think is clear or not. You will not change the way people vote. The best path is probably just to edit the question to increase clarity and vote to re-open. $\endgroup$ Commented Jan 11 at 1:48
  • $\begingroup$ @hft Yes, that is the plan, and the reason I asked this question. As I read it as clear and nobody who understands the topic of the question provided feedback in the comments, I sought the information here. $\endgroup$ Commented Jan 11 at 1:58

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Well… the question refers to a $\Delta \phi$ but there is no such symbol in the figures. The figures have $\phi_i$ or $\Phi$ which I presume are the same as $\phi$.

The horizontal axis is $x$ but in fact (I guess) the first figure is really two figures merged into one so the horizontal axis does not continue. The potential is supposed to be linear in $x$ but there are parts of this figure where the energy does not increase with $x$. So I suspect the figures assume there’s some $\vec E$-field in only the region where the energy curves have a slope.

There is not much to tie the second figure with the first and in fact the second is confusing because the first at least shows the final Fermi energy not at the same level as the initial Fermi energy. Maybe why this is so is what the question is about.

I did not vote-to-close but whenever I read “I have seen” or “I have read” I always wonder where because of the possibility of finding the original source and provide readers additional details left out by the OP.

I realize the OP lifted the figures and they are meant to be illustrative, but I actually think there some info missing in particular w/r to the connections between the figures. I have colleagues who work on this topic so they would have no issues understanding the figures because the know all the assumptions common to the field, but the difficulty is that the OP doesn’t understand something and it’s not clear (to me anyways) upon reading how figures illustrate what they do not understand.

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  • $\begingroup$ "So I suspect the figures assume there’s some E⃗ -field in only the region where the energy curves have a slope." This is the problem I'm talking about. If you understood the topic you wouldnt have to assume. There only is electric field in regions of nonzero slope. That is how band diagrams work. The question very well may be unclear to someone unfamiliar with the field. But it is clear to those who are, whom are the target audience. $\endgroup$ Commented Jan 11 at 1:07
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    $\begingroup$ Actually if the question is only clear to a (small) target audience then it is IMO in need of clarity as the site should appeal to an audience beyond the niche specialist: the site is not meant as a collection or collage of conversations between specialists. How broad or narrow is debatable but in this case the question could use details, if only sourcing the images or giving textbook references. $\endgroup$ Commented Jan 11 at 3:54
  • $\begingroup$ I may need to write up another question about that then because that just doesn't seem workable. The vast majority of questions on this site are unclear to me because I don't have the requisite background understanding. But up until your comment here that seemed fine. I'm not suggesting we are discussing some absurdly niche topic though. I was just expecting that questions about semiconductor physics are permitted (as was done in this case) to assume at least an undergraduate introduction to semiconductor physics level understanding. I don't really understand how it could be any other way. $\endgroup$ Commented Jan 11 at 12:22
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    $\begingroup$ Its actually quite frustrating because all the feedback received on this question has come from people who are making statements that suggest they don't even have that introduction to semiconductor physics level understanding. Then declaring the question isn't clear. Questions can't be clear to everyone There are surely some fundamentals that must be permitted to be assumed. Otherwise everyone will have to spend pages and pages establishing the basics before getting into any kind of advanced topic. $\endgroup$ Commented Jan 11 at 12:26
  • $\begingroup$ Anyway, I incorporated the feedback I received here and proposed an edit. If that doesn't sufficiently clarify, I'm out of ideas. Thanks for your help. $\endgroup$ Commented Jan 11 at 12:54
  • $\begingroup$ You did a reasonable job with the edit actually: I'm not an expert so I do "understand" the question well enough to answer it, but your edit does help. I agree the situation can be frustrating (and circular: it can be difficult to explain something one does not understand) and I had a sense of what the figures meant but it is important for instance to match the notation of the figure with the notation in the text, correctly identify regions etc, i.e. provide details on the usual assumptions that go in a figure, be clear about the question... $\endgroup$ Commented Jan 11 at 15:07
  • $\begingroup$ ... and do as you did and ask for feedback when in doubt. A good number of questions are re-opened after serious edits, especially after 'lack of clarity" closures. $\endgroup$ Commented Jan 11 at 15:08

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