Employees of the Center for Radio Photonics and Microwave Technologies of MEPhI have created a new radiation-resistant and temperature-stable material for magnetic field Hall sensors. Sensors of this type are widely used to control the magnetic field in nuclear and thermonuclear installations (tokamaks), they are in demand in research projects of the Mega science class, where they are exposed to strong radioactive radiation.

Single crystal indium arsenide in plates

This makes it relevant to develop innovative materials that will increase the service life of measuring instruments in conditions of high background radiation. The results of the work of scientists are published in the Applied Surface Science journal. The project is supported by the Priority 2030 program.

According to the study, indium-containing semiconductor compounds - compounds of indium with antimony (indium antimonide, InSb) and arsenic (indium arsenide, InAs) are the most promising materials for creating sensors that work under harsh radiation conditions. Unlike other semiconductors, the electron concentration in indium arsenide crystals increases upon irradiation, since radiation defects of the donor type mainly arise in this substance when exposed to any type and any dose of hard radiation. Due to this property, under the influence of radiation, the electrical conductivity of the material does not fall, but only increases with time.

Sapphire was chosen as the substrate for the indium arsenide film, since it is one of the most resistant dielectric materials to ionizing radiation.

Silicon-doped indium arsenide films on sapphire substrates were obtained and studied for the first time in the world by molecular-beam epitaxy. The main problems in obtaining epitaxial films on a non-native substrate are the crystal structure and lattice period that differ from the substrate. The resulting indium arsenide films 100 nm thick have a good mobility of 600 cm2/V s, as well as excellent thermal stability of conductivity: the resistance of the material in the range of 4–320 K changes by less than 1%.

The results obtained demonstrate the potential for implementing thermally stable InAs-based magnetic field sensors based on the Hall effect, as well as for creating field-effect transistors.