Researchers at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) in Bengaluru, an autonomous institution under the Department of Science and Technology (DST), have made a groundbreaking discovery in the field of semiconductors. The team has demonstrated a rare electron localization phenomenon, which the Ministry of Science and Technology announced could significantly broaden the scope of semiconductor applications.
This remarkable discovery has the potential to enhance the performance of existing semiconductors and expand their uses in various high-tech fields such as lasers, optical modulators, and photoconductors. Led by Associate Professor Bivas Saha, the researchers have revealed how single-crystalline, highly compensated semiconductors can undergo a significant metal-insulator transition, using single-crystalline scandium nitride as a key example. This work involved collaboration with researchers from the University of Sydney in Australia and the Deutsches Elektronen-Synchrotron in Germany.
According to Professor Saha, the research demonstrates a phenomenon akin to the Anderson transition, which typically occurs in disordered systems, but here it is observed in a single-crystalline material. Published in the journal Physical Review B, the findings reveal an astonishing nine orders of magnitude change in resistivity, shedding new light on electron localization within these materials.
The researchers utilized oxygen and magnesium as random dopants to induce what they describe as a “quasi-classical Anderson transition.” This transition creates fluctuations in electrical potential, resulting in electron-rich regions within a dielectric matrix. These regions bring about a band structural change in the parent material, leading to a percolative metal-insulator transition. Interestingly, while the material’s structure remains unchanged, it experiences a significant electronic transition.
Anderson localization, a wave phenomenon that applies to various types of wave transport—including electromagnetic, acoustic, quantum, and spin waves—underpins this transition. The random distribution of dopants causes potential fluctuations, which increase the semiconductor’s resistivity by localizing charge carriers. In these localized systems, electron transport occurs through a percolation process, a phenomenon that is not commonly observed in semiconductors. Consequently, the physics governing electrical transport, as well as properties like mobility, photoconductivity, and thermopower, differs significantly in such materials.
Dr. Dheemahi Rao, the lead author of the study, emphasized that this electronic transition in single-crystalline and epitaxial semiconductors could pave the way for their among the many uses for this technology are photorefractive dynamic holographic media, optical modulators, photoconductors, lasers, and spintronic devices. These findings suggest that manipulating potential fluctuations could become a novel tool for altering the properties of semiconductors, potentially leading to more efficient materials for various scientific and technological applications.
