Hall Effect Modulation via Ionic Gating in Degenerate Oxide Semiconductors

Hall measurements, a cornerstone technique for probing semiconductor properties, provide critical insights into the carrier concentration and mobility under magnetic fields. However, its application in materials with high intrinsic electron density, such as degenerate semiconductors, is often hindered by inherent electric field screening effects that obscure carrier behavior. Likewise, traditional gating methods struggle to effectively modulate carrier density in these materials, thereby limiting deeper exploration of solid-state physics phenomena. Here, we demonstrate that water-in-salt electrolyte-mediated ionic gating effects induce an unconventional Hall response in indium-tin oxide, enabling the observation of a metallic-to-semiconducting shift. Through in situ Hall measurements, we quantitatively analyze distinct charge modulation patterns that lead to substantial modifications in the energy band structure of the material. This work provides a framework for unraveling the complexities of ionic gating effects in degenerate semiconductors. Ultimately, this study facilitates broader characterization of emerging semiconductor materials and their prospective applications in advanced electronic devices.