Physicists from Krasnoyarsk have found that the electrical resistance under the action of a magnetic field in semiconductor structures depends on the presence of impurities in silicon substrates. Scientists have demonstrated how adding additional impurities can improve the efficiency and temperature conditions of the effect. The research results are published in the journal Materials Science in Semiconductor Processing.

In modern microelectronics, silicon-based devices are widely used. In particular, many field-effect transistors, solar cells and photodetectors are made in the form of multilayer structures of a metal, a dielectric and a semiconductor. Such composite materials are characterized by high magnetoresistance, a change in electrical resistance under the influence of a magnetic field, which expands the functionality of semiconductor devices.

Krasnoyarsk scientists have determined that the manifestation of magnetoresistance in structures consisting of a metal, a dielectric and a semiconductor depends on the impurities included in the semiconductor. Researchers have also learned how to artificially create this effect at elevated temperatures by adding other impurities to the semiconductor, and how to control it using magnetic and electric fields.

Scientists previously observed magnetoresistance in semiconductor structures. But they didn't know what was causing it. Having begun to study in more detail the substrates included in these structures, they determined that the effect manifested itself in the form of an abrupt increase in the electrical resistance of the material at low temperatures under the influence of a magnetic field. In a new study, physicists studied a silicon sample in which they added gallium to a standard boron impurity. In this material, an additional "jump" in resistance appeared at higher temperatures.

“We have been researching magnetoresistance in doped semiconductors for a long time. Earlier, we discovered the appearance of magnetoresistance, but its nature was not entirely clear to us. Studying a metal-insulator-semiconductor structure, we came to a conclusion that resistance arises due to impurities in the silicon substrate. Gallium implanted into a semiconductor showed itself to be equal to standard impurities that were already in the substrate. Our studies show that the physical properties not only of the usual boron impurity, but also the implanted gallium impurity depend on the magnetic field, which causes magnetoresistance, ” says Anton Tarasov, Candidate of Physical and Mathematical Sciences, researcher at the laboratory of radiospectroscopy and spin electronics at the L.V.Kirensky Institute of Physics SB RAS.

In addition, the physicists found that turning on a magnetic field parallel to the plane of a sample can control the effect. In this case, it manifests itself at higher temperatures. In addition, the second impurity in the substrate increased the magnetoresistance to the maximum possible value. As the scientists note, the ability to "adjust" the effect is important for the prospects for its application.

“In the future, we want to use other impurities or semiconductors and to try to achieve the effect at room temperature. At the moment, it manifests itself only at temperatures below -200 degrees Celsius, ” explains Dmitry Smolyakov, Candidate of Physical and Mathematical Sciences, researcher at the laboratory of radiospectroscopy and spin electronics at the L.V.Kirensky Institute of Physics SB RAS.

Scientists note that the effect of magnetoresistance and the discovered effects can be used in the development and manufacture of electronic devices, for example, sensors and magnetic field sensors. Such devices can be found in hard disks of computer memory and in mobile phones.

The study was carried out with the financial support of the Megagrant of the Government of the Russian Federation for the creation of world-class laboratories (No. 075-15-2019-1886).

The implantation was performed at the Scientific Research Institute of Physics and Technology (SRIPT), and N.I. Lobachevsky Nizhny Novgorod State University.