AlN/GaN 异质结场效应晶体管中与应变分布相关的载流子散射机理研究

由于卓越的高频性能和E/D模兼容特性， AlN/GaN 异质结场效应晶体管（HFET）已成为国内外研究热点。AlN/GaN HFET中AlN势垒层在源、漏和栅金属作用下会出现应变梯度分布，从而对沟道载流子造成弹性散射，即极化梯度库仑场散射。目前，该散射机制的理论研究还远不够深入，特别是该散射机制对AlN/GaN HFET器件特性的影响知之甚少。由于AlN/GaN HFET势垒层很薄，源、漏和栅金属对势垒层应变的影响将更加显著。本项目拟研究材料结构（不同厚度的势垒层及GaN盖帽层）和器件工艺（不同源漏间距、栅长及钝化工艺）对AlN/GaN HFET 中AlN势垒层应变的影响，分析应变极化梯度库仑场散射对AlN/GaN HFET中沟道载流子迁移率的影响，结合薛定谔方程和泊松方程自洽计算，确立该散射机制的解析表达式，并用于指导材料器件设计，改善AlN/GaN HFET器件的频率特性。

Nowadays, AlN/GaN heterostructure field-effect transistors (HFET) have been the un-to-date subject of intense investigation due to their high frequency and compatible E/D mode applications. The soure/drain and gate metals together effect the strain of the AlN barrier layer of AlN/GaN HFET, thus, the polarization Coulomb field scattering related to irregularly distribution of polarization charges is formed attributed to partial strain relaxation in AlN layer. However, little attention has been paid to the theoretical research of the polarization Coulomb field scattering, especially the role that the polarization Coulomb field scattering plays in the up-to-date AlN/GaN HFET devices. The influence of soure/drain and gate metals on the strain of the AlN barrier layer is more obviously due to the thinner barrier layer. The goal of this Research Project is to investigate the influence of material structure (different thickness of AlN barrier layer and GaN cap layer) and device process (different soure-to-drain length, gate length and passivation) on the strain of the AlN barrier layer of AlN/GaN HFET, and to analyze the role that the polarization Coulomb field scattering plays in the AlN/GaN HFET devices. Further, the wave function of the two-dimensional electron gas (2DEG) in the AlN/GaN HFET and the matrix element of electron transitions are calculated by self-consistently solving Schrodinger's and Poisson's equations. Finally, the equation of the polarization Coulomb field scattering function is obtained based on the polarization-distribution model and calculated 2DEG scattering probability. Systemic investigation of polarization Coulomb field scattering is of great importance to optimize the material/device structure and device process for further improving the frequency of AlN/GaN HFET.