中文摘要：

N极性GaN材料借助与传统Ga极性GaN极性相反这一特征，以低接触电阻、高2DEG限阈性，在高频、大功率微波晶体管、增强型器件及传感器等应用方面显示出了极大的优势。首先分析了N极性GaN材料与HEMT器件的特性，指出了其和Ga极性材料与器件的区别及优势。同时研究了N极性GaN材料的生长、HEMT器件结构及性能发展趋势，分析表明随着材料生长及器件制作工艺水平的逐步提高，N极性GaN材料与HEMT器件性能提升很快。特别是AIN插入层的引入、A1GaN背势垒层si掺杂及Al组分渐变式处理，结合新型绝缘层、源漏凹槽、自对准与InN／InGaN欧姆再生、长颈T型栅、双凹栅槽等新技术，使N极性GaNHEMT器件小信号特性逐步提高。而MOCVD、MBE工艺在N极性GaN材料生长方面的优化，也促进了N极性GaNHEMT器件在C波段和X波段功率放大应用方面的进一步发展。

英文摘要：

By virtue of the polarity opposite to the conventional Ga-polar GaN, N-polar GaN materials, with lower contact resistance and better 2DEG confinement, show great advantages in the application in high frequency and high power microwave transistor, enhanced devices and sensors. Firstly, the characteristics of N-polar GaN materials and devices are analyzed, and the differences and advantages of N-polar GaN based materials and devices compared with that of Ga-polar are pointed out. Besides that, the growth of N-polar GaN materials and N-polar GaN based HEMTs device structures and performance trends are studied. Analysis results show that N-polar GaN materials and HEMTs develop fast along with the improvement of materials growth and devices process. Combined with the new technologies, such as new types of insulation layer, source and drain recess, self-aligned technology with InN/InGaN ohmic regrowth, tall-stem T-gate, double-gate-recess and so on, the small signal characteristics are gradually increased, especially depending on the introduction of A1N interlayer and A1GaN back barrier with Si dopant and A1 composition gradient. The further optimization of MOCVD, MBE techniques in the growth of N-polar GaN materials prompts the application of N-polar GaN HEMT devices in C band and X band power amplifiers.