三维栅结构氮化镓增强型器件研究

Due to continued innovation in material epitaxy technology, device fabrication process and device structure design, GaN HEMTs, especially microwave power devices, have made an extraordinary progress in terms of both performance and commercialization. Either for fail-safe operation or simple E/D digital integrated circuit design, enhancement-mode (E-mode) devices are of great necessity. Still, fabrication techniques, which allow for obtaining high performance E-mode HEMT with simplicity and low-cost, remain challenging. Traditional threshold-modulation approaches realize a transition from the normally-on operation to normally-off one, relying on depleting 2DEG only from the vertical direction perpendicular to the AlGaN/GaN heterojunction. In order to break the limit set by 2D planar structure, we are intended to innovatively introduce the advanced concept of well-developed Si finFET into GaN semiconductor system (called finHEMT) in the program. Specifically, the project aims at achieving high performance E-mode HEMT by breaking through the key process of nanochannel formation, optimizing finHEMT device structures, designing novel heterojunctions and combining the conventional techniques effectively; furthermore, with the help of 3D TCAD simulation, the modulation rule and operation mechanism inherent of finHEMT will be disclosed, and finally a complete E-mode finHEMT system comprised of fabrication process, device structure and basic physical theory will be expectedly established in success, as a result, substantially promoting the practicality of GaN based E-mode devices.

得益于材料外延、器件工艺以及器件结构的不断创新，氮化镓基电子器件，尤其是微波功率器件，近几年在性能和商业化方面都取得了巨大进步。然而，为获得电路的“失效-安全”工作，简化数字集成电路结构，氮化镓增强型器件是必不可少的基本单元，能够简单、高效地获得高性能增强型器件是目前氮化镓基器件面临的最大挑战。传统阈值调节技术，通过从垂直于异质结方向降低电子浓度，实现从耗尽型向增强型的转变。为突破二维平面结构的限制，本项目拟将Si基FinFET先进的三维栅概念引入到氮化镓半导体中（GaN FinHEMT），通过突破异质结沟道形成的关键工艺技术，提出优化的三维栅结构，改进异质结结构，并有机结合传统技术，实现高性能增强型器件；进一步，结合3D TCAD仿真，揭示三维栅增强型器件内在的调制规律、工作机制，探索建立完整的三维栅增强型器件工艺、结构和理论体系，从而对氮化镓增强型器件的实用化进程起到重要的推动作用。

为获得开关电路的“失效-安全”工作，简化数字集成电路结构，氮化镓增强型器件是必不可少的基本单元，能够简单、高效地获得高性能增强型器件是目前氮化镓基器件面临的最大挑战。传统阈值调节技术，一般通过从垂直于异质结方向降低电子浓度，实现从常开型向增强型的转变，这种简单的方式导致器件阈值电压与饱和电流间难以平衡的矛盾。为突破这种限制，本项目开展了三维栅结构氮化镓增强型器件研究，利用侧栅引入的横向耗尽作用，实现氮化镓增强型器件的突破。具体而言，本项目突破了纳米级异质结沟道形成的关键工艺技术，揭示了纳米Fin 宽度、间隔等结构参数对器件性能的依赖关系（包括阈值电压、跨导、频率等）与电流输运机制；研制出国际首支氮化镓高线性三维结构微波功率器件，兼具高线性度、高功率密度和热管理能力等优势，是对传统GaN二维平面结构的重要创新，可广泛应用于射频尖端电子装备及下一代无线通信；提出了“槽栅+自对准纳米三维结构”的复合增强型器件，实现了饱和电流超过800mA/mm、阈值电压为+1V的高性能增强型绝缘栅器件。总之，通过本项目的实施，初步建立起GaN三维栅耗尽型与增强型器件工艺、结构和理论体系，从而对三维栅结构氮化镓器件在射频与电力电子领域的实用化进程起到重要的推动作用。