Team of Wang Xinqiang, Wang Ping, and Wang Tao from Peking University makes significant progress in the research of wurtzite nitride ferroelectric semiconductors

Recently, a team of researchers from Peking University's School of Physics, Institute of Condensed Matter Physics and Materials Physics, Center for Wide Bandgap Semiconductor Research, State Key Laboratory of Artificial Microstructures and Mesoscopic Physics, and the Frontier Science Center for Nano-Optoelectronics, led by Wang Xinqiang, Wang Ping, and Wang Tao (from Peking University's Electron Microscopy Laboratory), experimentally revealed the physical origin and control methods of the interfacial dead layer in wurtzite nitride ferroelectric semiconductors. Their findings, titled "Unveiling Interfacial Dead Layer in Wurtzite Ferroelectrics," were published in Nature Communications on July 2, 2025.

Wurtzite nitride ferroelectric semiconductor materials, such as ScAlN, ScGaN, YAlN, and BAlN, possess a stable ferroelectric phase, high Curie temperature, large remnant polarization, tunable coercive field, strong piezoelectric properties, and high compatibility with silicon-based and gallium nitride-based semiconductor processes. These materials are considered ideal candidates for next-generation micro-nanoelectronics, acoustic, and optoelectronic devices. Despite significant recent progress in material preparation and device development, challenges remain, including difficulties in thickness reduction, severe polarization fatigue, and significant current leakage. These phenomena are closely related to the "dead layer" affecting interfacial ferroelectric polarization control. However, experimental evidence regarding the formation mechanism and control methods of the interfacial dead layer has been lacking.

To address this scientific and technological issue, the Peking University team conducted an in-depth atomic-scale study of single-crystal ferroelectric ScAlN/GaN heterostructures grown by molecular beam epitaxy. Experiments revealed that the failure of ferroelectric polarization control near the ScAlN/GaN heterointerface originates from the combined effects of high-density nitrogen vacancies and interfacial compressive strain formed during growth. Theoretical studies showed that compressive strain reduces the formation energy of nitrogen vacancies, leading to their accumulation near the interface during ScAlN thin film growth, consistent with experimental observations. The formation of high-density nitrogen vacancies not only degrades the dielectric properties of the material but also increases the polarization reversal barrier, with compressive strain further exacerbating the latter. These combined effects suppress the reversibility of ScAlN polarization near the interface, leading to ferroelectric polarization control failure. This work elucidates the microscopic origin of the interfacial failure in wurtzite nitride ferroelectric semiconductors and highlights the importance of defect and strain engineering for expanding their applications in advanced electronic, optoelectronic, photonic, and acoustic devices. This lays the foundation for future large-scale applications in advanced non-volatile memory, neuromorphic computing, radio frequency communication, and optoelectronic/acoustoelectronic integration.

Figure 1. Single-crystal ferroelectric ScAlN/GaN heterostructure grown by molecular beam epitaxy.

Figure 2. Reversible atomic displacement during polarization reversal in ferroelectric ScAlN.

Figure 3. Interfacial polarization control dead layer and its microstructure in ferroelectric ScAlN.

Figure 4. Effect of nitrogen vacancies on ferroelectric ScAlN.

Figure 5. Relationship between strain, nitrogen vacancies, and polarization reversal barrier in ferroelectric ScAlN.

Wang Jinlin (Peking University, Class of 2019 PhD student), Li Yunqin (East China Normal University, Class of 2023 PhD student), Wang Rui (Peking University, Associate Researcher), Liu Qi (Peking University, Class of 2023 PhD student), and Ye Haitian (Peking University, Class of 2020 PhD student) are the co-first authors of the paper. Wang Ping, Wang Tao, Tong Wenyi (East China Normal University Researcher), and Wang Xinqiang are the corresponding authors. Professor Shen Bo, Professor Li Xinzheng, Associate Researcher Liu Fang, Assistant Researcher Sheng Bowen, and Dr. Yang Huaiyuan from Peking University, Professor Duan Chungang from East China Normal University, and Researcher Tong Yi from Suzhou Laboratory provided important guidance and support for this work.

This research was supported by the National Key Research and Development Program, the National Natural Science Foundation of China, the Beijing Natural Science Foundation, the Suzhou Laboratory Research Fund, the China Postdoctoral Science Foundation, the Shanghai Pujiang Program, Peking University's State Key Laboratory of Artificial Microstructures and Mesoscopic Physics, the Frontier Science Center for Nano-Optoelectronics, and Peking University's Electron Microscopy Laboratory.

Link to the original paper: https://doi.org/10.1038/s41467-025-61291-2