氮化镓异质结晶体管电荷控制能量模型与新结构

Charge Controlled Energy (CCE) concept has been proposed for the forward and reverse degradation in AlGaN/GaN HFET. It is used to reveal the nature of inherent contradictions between breakdown voltage and current collapse.There are two major innovations in this study:1.The distribution of electric field and elastic energy can be derived by solving the two-dimensional Possion equation.The internal relations of charge, electric field, and elastic energy can be studied for obtaining the charge modulation elastic energy principle. This principle means that the charge is used to modulate the electric field, and then to modulate the elastic energy. The mechanism of the degradation can be clarified by the Charge Controlled Energy Model(CCEM). The CCEM provides new ideas and theoretical basis for improving breakdown voltage and suppressing of current collapse.2. Based on CCEM, a novel enhancement-mode AlGaN/GaN HFET with charge compensation layer is proposed.There are three features: enhancement-mode channel, charge compensation layer, and high-κ dielectric layer.This structure can enhance the breakdown voltage and suppress the current collapse effect by suppressing of carrier injection, reducing surface electric field peak, decreasing of surface state density, etc., to offset the shortcomings of conventional devices. This study is of great significance as a fundamental and innovative research with international advanced level.

针对AlGaN/GaN HFET正反向退化问题，提出电荷控制能量（CCE）概念，揭示耐压和电流崩塌内在矛盾的物理本质。含两个主要创新点：1、通过求解二维泊松方程，导出异质结势垒层的电场和弹性能分布，探索电荷--电场--能量三者内在联系，获得电荷调制弹性能的原理，即电荷调制电场，最终实现调制弹性能。电荷控制能量模型阐明了器件退化机制，为提高耐压和抑制电流崩塌提供新思路和奠定理论基础。2、在该模型指导下，提出具有电子补偿层增强型AlGaN/GaN HFET新结构。所提结构具有三大特点：增强型沟道、电荷补偿层以及高k介质层。该结构从抑制载流子注入、减低表面电场峰值、减小表面态浓度等方面，有效提高了耐压和抑制电流崩塌，弥补了传统结构之不足。本申请是一项具有国际先进水平的基础性和开拓性研究，意义重大。

本项目试图建立在“电荷控制能量”的问题。课题组首先从多层异质结结构为切入点，采用空间电荷分离的可叠加的方法，将复杂的界面电荷问题转化成多个线电荷分布，然后通过保角变换实现结构的简化泊松方程形式，重点研究了电荷补偿结构的栅极边缘处电场解析表达式，获得了空间电场求解的方案，解决了“电荷控制能量”建立的电场的关键问题。在此优化电场模型的解决方案基础上，提出了可提高耐压的优化异质结新型器件。课题组下一步将针对完善“电荷控制能量”模型的验证进行研究。基于该模型的法研究方案对后续研究异质结型功率器件有启示意义。课题组共发表学术论文4篇（另已录用1篇于2018年1月）,获得授权发明专利5项，国际会议1篇，参编1本专著中两章（一共九章）。

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