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Semiconductor researchers discover effect that was thought impossible

in the journal Semiconductor Science and Technology . Semiconductor light sources, such as lasers and LEDs, are at the heart of modern technology. They enable laser printers and high speed internet. But only 60 years ago, no one would think that semiconductors were used as materials for strong light sources. The problem was that to generate light, such devices require electrons and holes – the free charge carriers of any semiconductor to be recombined. The higher the concentration of electrons and holes, the more often they are recombined, which makes the light source brighter. However, for a long time no semiconductor device could be manufactured to give a sufficiently high concentration of both electrons and holes. The solution was found in the 1960s by Zhores Alferov and Herbert Kroemer. They suggested using heterostructures, or "sandwich" structures, consisting of two or more complementary semiconductors instead of just one. Placing a semiconductor between two wider band gap semiconductors and applying a bias voltage, the concentration of electrons and holes in the intermediate layer can reach values ​​greater than those in the outer layers. This effect, called superinjection, is the basis for modern semiconductor laser and light emitting diodes. Its discovery earned Alferov and Kroemer the Nobel Prize in Physics in 2000. However, two arbitrary semiconductors cannot create a viable heterostructure. The semiconductors need to have the same period of the crystal grating. Otherwise, the number of defects at the interface between the two materials will be too high and no light will…

in the journal Semiconductor Science and Technology .

Semiconductor light sources, such as lasers and LEDs, are at the heart of modern technology. They enable laser printers and high speed internet. But only 60 years ago, no one would think that semiconductors were used as materials for strong light sources. The problem was that to generate light, such devices require electrons and holes – the free charge carriers of any semiconductor to be recombined. The higher the concentration of electrons and holes, the more often they are recombined, which makes the light source brighter. However, for a long time no semiconductor device could be manufactured to give a sufficiently high concentration of both electrons and holes.

The solution was found in the 1960s by Zhores Alferov and Herbert Kroemer. They suggested using heterostructures, or “sandwich” structures, consisting of two or more complementary semiconductors instead of just one. Placing a semiconductor between two wider band gap semiconductors and applying a bias voltage, the concentration of electrons and holes in the intermediate layer can reach values ​​greater than those in the outer layers. This effect, called superinjection, is the basis for modern semiconductor laser and light emitting diodes. Its discovery earned Alferov and Kroemer the Nobel Prize in Physics in 2000. However, two arbitrary semiconductors cannot create a viable heterostructure. The semiconductors need to have the same period of the crystal grating. Otherwise, the number of defects at the interface between the two materials will be too high and no light will be generated. In a way, it would be like trying to screw a nut on a bolt whose thread height does not match the nut. Because homostructures consist of only one material, part of the unit is a natural extension of the other. Although homostructures are easier to manufacture, homostructures were thought to not support superinjection and therefore not a viable basis for practical light sources.

Igor Khramtsov and Dmitry Fedyanin of the Moscow Institute of Physics and Technology made a discovery that drastically changes the perspective on how light emitting devices can be designed. The physicists found that it is possible to achieve super injection with just one material. In addition, most known semiconductors can be used.

“In silicon and germanium, superinjection requires cryogenic temperatures, and this doubts the effect of the effect. But in diamond or gallium nitride, strong superinjection can occur even at room temperature,” says Dr. Fedyanin. According to the new paper, superinjection can produce electron concentrations in a diamond diode that is 10,000 times higher than those previously thought to be final. As a result, diamonds can serve as the basis for ultraviolet LEDs thousands of times brighter than the most optimistic theoretical calculations predicted. ” The effect of superinjection in diamond is 50-100 times stronger than that used in most mass market semiconductor lamps and lasers based on heterostructures, “Khramtsov pointed out. ndsgap semiconductors for new two-dimensional materials. This opens up new opportunities for designing high-efficiency blue, violet, ultraviolet and white LEDs as well as light sources for optical wireless communication (Li-Fi), new types of lasers, transmitters for quantum internet and optical units for early disease diagnosis.


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More information:
Igor A Khramtsov et al., Superinjection in Diamond Homojunction P-I-N diodes, Semiconductor Science and Technology (2019). DOI: 10,1088 / 1361-6641 / ab0569

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Moscow Institute of Physics and Technology

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Semiconductor Researchers Discover Impact That Thought Impossible (2019, April 23)
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