BiFeO3-AlGaN/GaN异质外延生长及AlGaN/GaN二维电子气调控研究

The integration of ferroelectric film with wide band-gap semiconductor is the key technology for future applications in power electronics and smart sensor systems. In this project, we propose to achieve high-quality epitaxial BiFeO3 multiferroic films on AlGaN/GaN heterojunctions and intensively study the domain matching epitaxial mechanism. The interfacial coupling effect between the ferroelectric polarization of BiFeO3 and the piezoelectric polarization of AlGaN/GaN will be explored both experimentally and theoretically, to reveal the modulation of the two-dimensional electron gas (2DEG) at AlGaN/GaN interface through the strain effect and ferroelectric field effect of BiFeO3 films. The Metal-Ferroelectric-Semiconductor High Electron Mobility Transistors (MFSHEMT) will be developed with BiFeO3 films as the ferroelectric gate and the AlGaN/GaN 2DEG as the channel. The ferroelectric polarization status in BiFeO3 can be controlled by adjusting the structure and composition of the film, which can further modulate the 2DEG density and distribution in the AlGaN/GaN channel. On the basis of ferroelectric-modulation of 2DEG channel, MFSHEMT with high breakdown voltage, low gate leakage current, controllable threshold voltage will be further demonstrated, laying the foundation for improving the performance and design freedom of AlGaN/GaN high electron mobility transistor, promoting the development of multi-functional and practical devices.

铁电薄膜与宽禁带半导体的集成是面向功率电子、智能传感等新兴高技术产业应用的关键技术。本项目拟在AlGaN/GaN异质结表面外延生长BiFeO3多铁薄膜，深入研究外延生长机理与界面晶格匹配机制。结合实验研究与理论模拟，阐明BiFeO3的铁电极化与AlGaN/GaN的压电极化之间的相互作用机制，揭示BiFeO3薄膜的应变场、铁电场效应对AlGaN/GaN界面二维电子气的调制规律。在此基础上，以BiFeO3薄膜为极性栅介质，AlGaN/GaN二维电子气为导电沟道，制备铁电场效应高迁移率晶体管（MFSHEMT）。通过控制薄膜的铁电极化特性，实现对AlGaN/GaN界面二维电子气的精确调控，试制出击穿电压高、栅极漏电流低、阈值电压可控的MFSHEMT器件，为提高AlGaN/GaN高迁移率晶体管的性能和设计自由度，促进器件的多功能化和实用化发展奠定基础。

基于高性能铁电薄膜在GaN基半导体上的外延设计，研究铁电极化与AlGaN/GaN异质结界面二维电子气(2DEG)的耦合机理，探索铁电栅基增强型高电子迁移率晶体管(High Electron Mobility Transistor， HEMT)，对开发高性能GaN基功率电子系统具有重要研究价值。在本研究中，采用缓冲层技术实现铁电薄膜在GaN基半导体上较高质量外延集成，以FE/AlGaN/GaN铁电-半导体异质结为基础，系统揭示铁电极化与界面2DEG的耦合规律，通过调控铁电薄膜的极化状态实现了对于界面2DEG的完全耗尽，制备了铁电栅基增强型HEMT器件。具体在材料设计、物理机制和器件研究方面的创新性结果如下：.(1) 基于界面晶格缓冲层设计，诱导了钙钛矿型BiFeO3(BFO)铁电薄膜在纤锌矿型GaN基半导体上的外延集成，系统揭示了晶格匹配机制及外延生长机理，通过Mn元素掺杂处理外延集成了具有较高剩余极化强度的BFMO铁电薄膜。.(2) 设计了磁性CoFe2O4(CFO)缓冲层诱导钙钛矿型铁电薄膜BaTiO3(BTO)在纤锌矿型GaN半导体上外延生长，实现了BTO/CFO磁电异质结在GaN半导体上的直接外延构筑，且该异质结表现出良好的磁电功能特性。.(3) 基于BTO铁电栅层材料和界面晶格设计，构筑了BTO/MgO/AlGaN/GaN/Si铁电-半导体异质结，系统揭示了BTO中铁电极化与AlGaN/GaN界面2DEG的耦合机理，通过改变BTO铁电极化状态实现了对于异质结阈值电压由-0.4 V到+3.2 V范围内的可控调控，证明了铁电栅基增强型HEMT器件的可行性，并以上述异质结为基础制备了铁电栅基HEMT器件。.(4) 在AlGaN/GaN异质结上设计并高质量外延设计了具有高空穴浓度、宽禁带的Ni1-xLixO薄膜，发现了p型氧化物与GaN间的能带匹配特性是决定异质结阈值电压的关键因素，揭示了p型氧化物栅极材料的设计规则。.综上所述，本研究对于开发高性能铁电栅基增强型HEMT器件及相关功能集成器件具有重要指导意义。基于上述研究，目前已发表5篇SCI论文，申请5项发明专利。