Russian physicists were able to solve the problem of creating far infrared laser radiation in semiconductor structures. To do this, they created quantum wells from cadmium-mercury telluride. The results were published in ACS Photonics journal.
In a conventional semiconductor diode laser, radiation occurs during recombination - the mutual annihilation of electrons and holes. But the emission of radiation of a certain range is far from the only effect of this process.
Part of the energy during such recombination can be spent on increasing the energy of the surrounding electrons. This process of "wasting" electron-hole pairs into heat is called Auger recombination - in honor of the French physicist Pierre Auger, who discovered this effect.
The rate of the Auger process increases strongly in semiconductors with a small band gap. But it is these materials that are needed to create far infrared lasers. And it is these lasers that are in demand in studies of biological objects and problems of gas spectroscopy.
Researchers from the Moscow Institute of Physics and Technology and the Institute of Physics of Microstructures of the Russian Academy of Sciences in Nizhny Novgorod have proposed a way to get around this effect. According to the results of their research, cadmium-mercury telluride can become the optimal material for laser applications.
Previous experiments with this material have confirmed the possibility of creating radiation with a wavelength of up to 20 microns. But the calculations of the authors have shown that this is not the limit, and the radiation wavelength can be increased to 50 microns. The wavelength range from 30 to 50 microns is the most "forbidden" for existing semiconductor lasers based on elements of groups III and V of the periodic table due to strong self-absorption. But this negative effect - like Auger recombination - is greatly weakened in mercury telluride, this time because of the large mass of atoms that make up the crystal lattice. Therefore, researchers consider the new material to be promising for use in laser technologies.
Author: Nikita Shevtsev
