基于纵向短栅极沟道结构的低导通电阻常关型GaN基HEMT器件制备研究

As an important candidate in the field of power electronics devices, GaN-based HEMTs are very promising in various civil and military applications, such as electric vehicle, photovoltaic (PV) inverter, and radar systems. They exhibit high power density and high frequency owing to the existence of high-density and high-mobility 2-dimensional electron gas (2DEG) originated from the heterojunction structure. However, there are still a few key technical issues in the development of GaN-based HEMT device products. One of them is how to develop the normally-off devices with stable and high threshold voltage without increasing the device on-resistance. To solve this issue, a novel gate structure with a vertical and shortened channel is proposed for the first time in this project. By employing the proposal, the HEMT on-resistance is reduced as the gate channel is shortened remarkably compared with the conventional lateral HEMT gate structure. Meanwhile, stable and high threshold voltage will be achieved because the gate 2DEG channel is cut off completely and the etching process at GaN surface is optimized. The proposal will hence endow the devices with both low on-resistance and high threshold voltage. In this project, all the theoretical simulation, material growth, and device fabrication work will be conducted, with the focus on device parameter optimization, high-resistivity GaN growth, and fabrication of fine gate structure. The device target is low on-resistance (＜2mΩ•cm2), high threshold voltage (＞3V), and high breakdown voltage (＞600V). The proposal will provide a new perspective in developing normally-off HEMT devices.

作为现代电力电子器件的重要代表之一，GaN基HEMT器件在电动汽车、光伏逆变器以及雷达等民用和军用领域都有非常重要的应用前景。然而，目前研制GaN基HEMT器件过程中还存在若干技术问题，其中关键问题之一就是难以获得高品质的常关型（增强型）器件，特别是在不明显增加器件栅极沟道电阻的前提下如何获得稳定可靠的大阈值电压，是一个国际性难题。针对这一难题，本项目提出切断二维电子气（2DEG）沟道并引入纵向短栅极沟道方案，开展新型纵向栅极结构HEMT器件研究。本项目采用仿真模拟、材料生长和器件制备相结合的方法深入开展研究，通过重点研究器件结构仿真与参数优化、非故意掺杂高阻GaN生长、栅极结构工艺优化以及器件特性分析等内容，获得稳定可靠的亚微米量级纵向短栅极沟道结构常关型HEMT器件，同时实现器件大的阈值电压和低的导通电阻。研究成果为常关型HEMT器件制作提供新思路，为其应用推广提供更多的技术储备。

氮化镓是最具潜力的新一代功率器件材料的重要代表之一，基于氮化镓材料制备的常关型HEMT器件具有安全、节能和简化电路设计等优点，在电动汽车引擎驱动和可再生能源发电系统等许多领域具有重要的应用前景。本项目针对在现有常关型器件制作技术路线下出现的难以同时获得低的器件导通电阻和高的阈值电压这一难题，提出了纵向短沟道新型HEMT器件制作方案，开展了器件理论设计与仿真模拟、器件工艺摸索、参数优化、芯片制作以及可靠性机理分析等研究内容，已经顺利完成研究目标，研究内容和成果超过预期。制作的器件阈值电压为2-5V，导通电流密度200-500mA/mm，击穿电压大于900V。在该项目经费支持下，项目负责人发表SCI收录一作（或第一通讯）论文7篇，EI收录一作论文2篇；授权发明专利3项，新申请发明专利9项；项目研究内容进一步拓展，申请并获批国家自然科学基金面上项目1项；指导的学生获得3人次国家奖学金和1人次硕士生学术之星。该研究成果为常关型HEMT器件制作提供新思路，为其进一步应用推广提供更多的技术储备。