【作者】 汪洁；

【导师】 孙玲玲；

【作者基本信息】 浙江大学 ， 电路与系统， 2013， 博士

【摘要】 氮化镓高电子迁移率晶体管(GaN HEMT)模型是GaN微波单片集成电路(MMIC)CAD的基础。现有的GaN HEMT物理模型未能解决载流子传输方程与新效应联立自洽求解带来的数值算法问题、异质结界面处量子力学效应和极化电荷处理的物理问题,难以表征多样的器件结构和复杂的物理效应。相比之下,基于表面势的物理模型可不断加入新物理效应的表征,将各种物理效应直接引入表面势方程,这样模型能更加精确的描述器件的物理本质。目前基于表面势模型研究尚在起步阶段,本文通过深入研究GaN异质结结构、器件物理特性的关联性,主要围绕基于表面势GaN HEMT紧凑型建模方法和技术展开。具体内容概括如下：1)从半导体理论和量子阱理论出发,分析各外延层结构基础上,将GaN HEMT器件特有的极化效应、费米势、势垒层掺杂等影响引入表面势方程,建立GaN HEMT器件表面势方程；并采用牛顿迭代法对GaN HEMT器件的表面势方程进行数值自洽求解,获得的表面势精确数值解验证了表面势方程的可行性。2)在GaN HEMT器件超越方程的解析求解、连续性函数和函数平滑因子开发等难点上取得了突破,避免了PSP电荷模型在积累区难以胶合的缺点；把全部工作区分为三个区重新推导体电荷密度,获得了全部工作区内连续、可导的电流电压(I-V)和电荷/电容电压(Q/C-V)特性方程；根据GaN HEMT器件的散射机制建立了新的迁移率模型；建立的紧凑型(Compact)内核模型实现了对电流和电荷/电容特性及一阶导数(跨导、电导、电容)以及高阶导数的拟合。TCAD工具仿真AlGaN/GaN HEMT和AlGaN/AIN/GaN HEMT两种结构器件的直流特性,TCAD仿真与模型仿真结果对比验证了基于表面势内核模型的准确性。3)在GaN HEMT紧凑型内核模型的基础上,提出了能准确表征器件高阶行为和高频寄生效应的模型拓扑结构,给出了模型参数以及模型参数提取方法,完成了一种基于表面势的GaN HEMT器件紧凑型模型。测试数据和模型仿真结果有很好的拟合,验证了GaN HEMT器件紧凑型模型的精确性。本文发展出基于器件物理机理和结构参数信息的表面势紧凑型模型和建模方法,在GaN HEMT器件基于表面势建模、电流及电荷/电容特性研究方面取得了较大的进展,为器件模型的开发提供了可信的方程形式,也为兼任数字、数模混合仿真用GaNHEMT器件模型的开发建立了基础。为了能精确描述器件实际行为并丰富模型的表征能力,不仅需要对模型进一步实用化的开发和经验/半经验化的处理,而且要不断拓展电流/电荷方程。更多还原

【Abstract】 Gallium Nitride High Electron Mobility Transistor (GaN HEMT) models are basics of the GaN Microwave Monolithic Integrated Circuit (MMIC) CAD. But the existed GaN HEMT physical models not only can’t solve the numerical computation problems which come from self consistently solving carrier transport equation and physcial problems which deal with the quantum effect and the polarization charge on the hetero-junction interface, but also can’t describe the variety of device structure and the complexity of the physical effects. By contrast, the surface potential based model is more accurately characterize the transistor physical essence which can add new physical effects to model and surface potential equation. Now the study on the surface potential model was still in the initial stage, this paper made an intensive study of GaN heterogeneous structure and relativity between physical characteristics, mainly focused on the the modeling method and technology based on the surface potential for GaN HEMT device. It can be summarized as follow:1) Based on the semiconductor theory and quantum theory, this paper analyze the device epitaxial layer structure. In this work, the effects of the polarization, the Fermi level and the doping in barrier are incorporated into the surface potential equation, and the surface potential equation for GaN HEMT was built; Numerical self consistent solutions of the equation were got by using the newton iteration method. The precise numerical solution of the surface potential verified the feasibility of the surface potential equation.2) The difficulties have been broken through, such as the building of the surface potential equation for GaN HEMT, the analytical solution of the transcendental equation, the exploitation of the continuous function and smoothing factor. This paper deduced the equation of the body charge density in new three regions which can avoid the hardly continuum of the PSP charge model, and got the continuous I-Vand C-v characteristic equations in all the work area; The new mobility model is built according to the scattering mechanisms of GaN HEMT device; The developed surface potential based compact core model achieved the fitting of the current and charge characteristics, first-order derivative (conductance, capacitance, trans-conductance) and higher-order derivative. The TCAD tools simulated the direct-current characteristic of GaN HEMT (AlGaN/GaN HEMT and AlGaN/AlN/GaN HEMT. Good agreement with TCAD simulations verified the accuracy of model.3) Based on GaN HEMT compact core model, this paper proposed the topology structure of the model which can accurately characterize high order behaviors and the high frequency parasitic effects, and the model parameters and the flow of the parameter extraction are presented. In he end, this paper developed a surface potential based compact model for GaN HEMT. The measured and modeled results have good fitting.The paper presented the surface potential compact model and modeling methods based on the physical mechanism and the structural.parameter information. It has made great progress in the surface potential modeling and the research of current and charge/capacitance characteristics. This work provided the credible forms of the equation and the theoretical basis to the modeling, and the base of GaN HEMT model which can be used for the digital signal, the digital and analog mixed signal simulation. To accurately describe the device practical behavior and enrich the representation ability, this model not only need be practical developed and empirical/semi empirical processed but also expanded the current equation and charge equation.更多还原