science

Negative luminescence

Negative luminescence is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Negative luminescence rather than just read about it. In short: Negative luminescence is a physical phenomenon by which an electronic device emits less thermal radiation when an electric current is passed through it than it does in thermal equilibrium (current off). When viewed by a thermal camera, an operating negative luminescent device looks colder than its environment.

Key takeaways

Negative luminescence belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Negative luminescence to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Negative luminescence from memory before moving on to harder problems.

Reference excerpt

Negative luminescence is a physical phenomenon by which an electronic device emits less thermal radiation when an electric current is passed through it than it does in thermal equilibrium (current off). When viewed by a thermal camera, an operating negative luminescent device looks colder than its environment.

Physics Negative luminescence is most readily observed in semiconductors. Incoming infrared radiation is absorbed in the material by the creation of an electron–hole pair. An electric field is used to remove the electrons and holes from the region before they have a chance to recombine and re-emit thermal radiation. This effect occurs most efficiently in regions of low charge carrier density. Negative luminescence has also been observed in semiconductors in orthogonal electric and magnetic fields. In this case, the junction of a diode is not necessary and the effect can be observed in bulk material. A term that has been applied to this type of negative luminescence is galvanomagnetic luminescence. Negative luminescence might appear to be a violation of Kirchhoff's law of thermal radiation. This is not true, as the law only applies in thermal equilibrium. Another term that has been used to describe negative luminescent devices is "Emissivity switch", as an electric current changes the effective emissivity.

History This effect was first seen by Russian physicists in the 1960s in A.F.Ioffe Physicotechnical Institute, Leningrad, Russia. Subsequently, it was studied in semiconductors such as indium antimonide (InSb), germanium (Ge) and indium arsenide (InAs) by workers in West Germany, Ukraine (Institute of Semiconductor Physics, Kyiv), Japan (Chiba University) and the United States. It was first observed in the mid-infrared (3-5 μm wavelength) in the more convenient diode structures in InSb heterostructure diodes by workers at the Defence Research Agency, Great Malvern, UK (now QinetiQ). These British workers later demonstrated LWIR band (8-12 μm) negative luminescence using mercury cadmium telluride diodes. Later the Naval Research Laboratory, Washington, D.C., started work on negative luminescence in mercury cadmium telluride (HgCdTe). The phenomenon has since been observed by several university groups around the world.

References Applications of negative luminescence, T. Ashley, C. T. Elliott, N. T. Gordon, T. J. Phillips and R. S. Hall, Infrared Physics & Technology, Vol. 38, Iss. 3 Pages 145-151 (1997) doi:10.1016/S1350-4495(96)00038-2 Negative luminescence and its applications, C. T. Elliott, Philosophical Transactions: Mathematical, Physical and Engineering Sciences, Vol. 359 (1780) pp. 567–579 (2001) doi:10.1098/rsta.2000.0743 Galvanomagnetic luminescence of indium antimonide, P. Berdahl and L. Shaffer, Applied Physics Letters vol. 47, Iss. 12, pp. 1330–1332 (1985) doi:10.1063/1.96270 Negative luminescence of semiconductors, P. Berdahl, V. Malyutenko, and T. Morimoto, Infrared Physics (ISSN 0020-0891), vol. 29, 1989, p. 667-672 (1989) doi:10.1016/0020-0891(89)90107-3

Patent U.S. patent 6,091,069, Ashley et al., July 18, 2000, Infrared optical system (Cold shield)

External links “Negative luminescence from InAsSbP based diodes in the 4.0-5.3 μm range” "Negative Luminescence in semiconductors"

Worked examples

Example 1 — a first encounter with Negative luminescence

Start with the simplest possible case. Write down what Negative luminescence claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Negative luminescence before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Negative luminescence ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Negative luminescence

In research: Negative luminescence appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Negative luminescence in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Negative luminescence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Infrared imaging, Luminescence, Semiconductors, so understanding it makes those chapters shorter.
In everyday life: Look for Negative luminescence outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Negative luminescence in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Negative luminescence means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Negative luminescence out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Negative luminescence in simple terms?

Why does Negative luminescence matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Negative luminescence?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Negative luminescence.