In cooperation with experts from the Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences (IMP UB RAS), researchers from the National Research Nuclear University MEPhI have developed and studied nanoheterostructures based on gallium arsenide, which can speed up the performance of high-frequency microcircuits.
Heterostructures are laminated materials made up of various semiconductors, which are traditionally used in electronic devices that are mounted on a substrate. Modern “quantum design” allows researchers to create semiconductors with the exact properties that are required for the production of state-of-the-art electronic devices.
To enhance the performance of a device, the content of indium in the active current-conducting layer of the material needs to be increased. By increasing the indium content, researchers decrease the mass of electrons in the structure which increases the speed, thus enhancing the performance of electronic devices. This process is, however, complicated by the mechanical stress in the crystal lattice of the adjacent layers.
Physicists at MEPhI have managed to solve this problem by building up the thick “transition” layer and steadily increasing the indium content in the active layer. As a result, the researchers have managed to increase it almost up to 100 percent while keeping the level of mechanical stress to a minimum.
To obtain samples, the researchers used epitaxial growth – the process of growing semiconductors that are perfect in terms of the crystalline structure on a “virtual substrate,” which gradually changes its crystalline lattice parameters as the transition layer grows.
Researchers had worked out the optimal conditions for the growing process: the temperature of the substrate, the structure of the transition layer, and the thickness and composition of the active layer. This allowed them to obtain high-quality structures with minimal electron scattering and low surface roughness (of only 2 nanometers).
Then the experts from IMP UB RAS measured the electronic properties of the samples created at MEPhI. To do that, they conducted research at low temperatures (from 1.8 K, or —271.35°С) in a powerful magnetic field. This allowed them to observe the quantum effects caused by the increased content of indium in the active layer of the sample, specifically, magnetoresistance oscillations and the quantum Hall effect: in 1985, a Nobel Prize in Physics was awarded for the discovery of this effect.
According to the experts, the data obtained by the Russian researchers, which was published in the Journal of Magnetism and Magnetic Materials”, can shed light on the peculiarities of the manifestation of the quantum Hall effect in modern nanostructures.
“This is, first and foremost, fundamental research,” said Ivan Vasilevsky, Associate Professor at the MEPhI’s Physics of Condensed Matter Department, and one of the authors of the article. “But we also see the potential of this application in practice: the fact that these structures have high electron mobility and ensure operation of transistors and microcircuits at high (up to 200 Ghz) frequencies.”