MOSCOW, December 8. A previously unknown effect of increasing the concentration of charge carriers in semiconductors during the study of gallium oxide was discovered by scientists from NNSU. According to the authors, the new knowledge is important for creating the next generation of devices for power electronics and other fields of technology. The results of the scientific work are presented in Applied Physics Letters.
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"Today, semiconductor materials are an integral part of analog and digital electronics. They are absolutely necessary for many industries,” said university experts.
As Alena Nikolskaya, a junior researcher at the Scientific Research Institute of Physics and Technology of Nizhny Novgorod State University, reported, due to the ever-increasing requirements for the operating power of electronic devices, the demand for so-called ultra-wide bandgap semiconductors.
“In semiconductor physics, the concept of “band gap” is used. It determines the electrical and optical properties of the material. As it increases, the value of the breakdown voltage increases, and, as a consequence, the maximum operating power of the device. The most interesting for practical application is gallium oxide β-Ga2O3 , whose band gap is very large — about five eV. For comparison: in silicon it is about one eV,» Nikolskaya explained.
Nizhny Novgorod State University researchers, together with colleagues from the Institute of Microstructure Physics of the Russian Academy of Sciences, discovered that during temperature treatment of a β-Ga2O3 crystal into which silicon atoms were added through ion implantation, an abnormally large increase in the number of electrons is observed, which exceeds the number of atoms silicon.
According to Nikolskaya, the introduction of dopant atoms is used to control the electrical properties of semiconductors. In traditional technologies, impurities are usually introduced using ion implantation (irradiation followed by annealing).
“We have established that at an annealing temperature of 800 degrees, almost complete activation of the silicon impurity in the β-Ga2O3 crystal occurs, that is, the number of added conduction electrons becomes almost equal to the number of embedded silicon atoms. With a further increase in the annealing temperature, the electron concentration continues to increase. We assume that during annealing, defect centers (groups of atoms) are formed in the crystal, which provide “extra” electrons,” she said.
According to the scientist, the team managed not only to achieve a concentration of electrons sufficient to create electrical devices, but also to exceed it due to the specifics of the processes occurring during implantation. This effect has never been observed anywhere in the world before.
The authors of the study suggest that the fundamental knowledge obtained will serve as a starting point for the creation of a new generation of devices for power electronics, deep ultraviolet photodetectors and other applications.
» Our team is faced with a world-class task — to establish the possibility of obtaining p-type («hole») conductivity in a β-Ga2O3 crystal. No one in the world has yet managed to obtain a stable, reproducible result in obtaining p-type Ga2O3,» Nikolskaya shared.< br />The work was supported by the Russian Science Foundation (grant No. 23-79-00052) and the Ministry of Science and Higher Education of the Russian Federation. UNN is a participant in the state support program for universities «Priority-2030» of the national project «Science and Universities».