Semiconductor scientists discover effect that was thought impossible

phys.org | 3/21/2019 | Staff
monna (Posted by) Level 3
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A physical effect known as superinjection underlies modern light-emitting diodes (LEDs) and lasers. For decades this effect was believed to occur only in semiconductor heterostructures—that is, structures composed of two or more semiconductor materials. Researchers from the Moscow Institute of Physics and Technology have found superinjection to be possible in homostructures, which are made of a single material. This opens up entirely new prospects for the development of light sources. The paper came out Feb. 21 in the journal Semiconductor Science and Technology.

Semiconductor light sources, such as lasers and LEDs, are at the core of modern technology. They enable laser printers and high-speed internet. But a mere 60 years ago, no one would imagine semiconductors being used as materials for bright light sources. The problem was that to generate light, such devices require electrons and holes—the free charge carriers in any semiconductor—to recombine. The higher the concentration of electrons and holes, the more often they recombine, making the light source brighter. However, for a long time, no semiconductor device could be manufactured to provide a sufficiently high concentration of both electrons and holes.

Solution - 1960s - Zhores - Alferov - Herbert

The solution was found in the 1960s by Zhores Alferov and Herbert Kroemer. They proposed to use heterostructures, or "sandwich" structures, consisting of two or more complementary semiconductors instead of just one. If one places a semiconductor between two semiconductors with wider bandgaps and applies a forward bias voltage, the concentration of electrons and holes in the middle layer can reach values that are orders of magnitude higher than those in the outer layers. This effect, known as superinjection, underlies modern semiconductor lasers and LEDs. Its discovery earned Alferov and Kroemer the Nobel Prize in physics in 2000.

However, two arbitrary semiconductors cannot make a viable heterostructure. The semiconductors need to have the same period of the crystal lattice....
(Excerpt) Read more at: phys.org
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