AlGaN/AlN/GaN电力电子器件中极化库仑场散射机制研究

The specific on-resistance and switching characteristic of the AlGaN/AlN/GaN power heterostructure field-effect transistors (HFETs) are closely related to the two-dimensional electron gas (2DEG) electron mobility and electron drift speed of the devices, and the different scattering mechanisms (polar optical-phonon scattering, interface roughness scattering, piezoelectric scattering and polarization Coulomb field scattering related to the strain variation of the AlGaN barrier layer) in the AlGaN/AlN/GaN power HFETs will affect the 2DEG electron mobility and electron drift speed of the devices. Based on the theoretical model of the polarization Coulomb field scattering under low electric field in AlGaN/AlN/GaN HFETs, we will study the influence of the passivation layer and the field plate structure on the strain variation of the AlGaN barrier layer and develop the theoretical expression of the polarization Coulomb field scattering in AlGaN/AlN/GaN power HFETs. Combined with the theoretical expression of polar optical-phonon scattering, interface roughness scattering, piezoelectric scattering and polarization Coulomb field scattering, we will analyse the influence of the all scattering mechanisms on the specific on-resistance and the switching characteristic. Finally, we intend to make the AlGaN/AlN/GaN power HFET devices with the specific on-resistance less than 2 mΩ•cm^2 and the value of the subthreshold swing less than 100mV/dec through optimizing the material and devices structure.

AlGaN/AlN/GaN电力电子器件的特征通态电阻和开关速度与器件的沟道载流子迁移率和载流子漂移速度息息相关，而器件中存在的各种不同的散射机制（极化光学声子散射、界面粗糙散射、压电散射以及与AlGaN势垒层应变相关的极化库仑场散射）会严重影响沟道载流子迁移率和载流子漂移速度。基于低电场下AlGaN/AlN/GaN HFETs器件中极化库仑场散射机制理论模型，开展AlGaN/AlN/GaN电力电子器件中钝化层和场板结构对AlGaN势垒层应变分布作用机制的研究，确立AlGaN/AlN/GaN电力电子器件中的极化库仑场散射理论解析表达式；结合其它散射机制解析表达式，研究分析各种散射机制对器件二维电子气（2DEG）沟道电阻和开关速度的影响机制；通过优化材料和器件结构，制作出特征通态电阻小于2mΩ•cm^2、亚阈值摆幅小于100mV/dec的AlGaN/AlN/GaN电力电子器件。

通过开展钝化层和场板结构对AlGaN/GaN电力电子器件势垒层应变影响研究，确立了AlGaN势垒层极化电荷分布，建立了钝化层和场板结构AlGaN/GaN电力电子器件中极化库仑场散射的理论模型，并得到了极化库仑场散射的解析表达式。理论模型计算得到的迁移率曲线与实验得到的数据吻合，证明了极化库仑场散射理论模型的正确性；基于理论模型，掌握了AlGaN/GaN电力电子器件中极化库仑场散射及其它散射机制对器件2DEG沟道电阻的影响规律认识；并通过优化设计钝化层和场板结构，制作出了特征通态电阻为1.82mΩ•cm^2、亚阈值摆幅为99mV/dec的AlGaN/GaN电力电子器件。.此外，为改善传统AlGaN/GaN电力电子器件栅极靠近漏极边缘易击穿问题，初步开展了激光触发大功率AlGaN/GaN开关研究，研制的激光触发大功率AlGaN/GaN开关工作电压可达到40kV，输出脉冲电流峰值达到350A。