作为第三代宽禁带半导体材料的代表，GaN在微波大功率应用领域发挥着独特优势并取得长足的发展。特别在近几年随着可靠性技术的突破，GaN功率器件实用化进程不断加快，对国民经济发展和国防能力能升的促进作用正日益显现。尽管如此，GaN体材料高电子饱和漂移速度和高击穿电压的优势尚未完全开发，其特有的极化效应以及体材料低维化引起的诸多深层次物理问题仍有待解决，深刻认识GaN基低维异质结构材料与器件特性之间的内在关系成为突破下一代GaN电子器件技术的瓶颈。本项目通过深入开展GaN基异质结构器件微观输运特性与材料极化、量子阱结构、子带分布、电子状态的关系研究，揭示二维载流子饱和漂移速度限制机理，并基于极化工程和二维能带裁剪设计，建立GaN高电子漂移速度异质结构材料和器件设计方法，实现ft≥200GHz的GaN HFET 器件，为完善氮化物半导体材料应用体系、发展新一代高频电子器件和电路奠定物理基础。

Gallium nitride, as one of the most attractive material of the third generation wide bandgap semiconductor, exhibit great potential for high-power microwave applications and have been extensively developed during the last decades. More recently, with rapid improvement of long-term reliability, the application process of GaN power devices and MMIC is speeding up, which plays a more and more imporpant role in improving the performance and functionality of national defence and economy. Although the extraordinary performance of GaN HFETs over those on traditional compound semiconductor,the physics behind the transport mechanism in the low dimensional III-nitrides heterostructure devices is still not completely understood. The advantage of the superior properties of GaN, such as high electron saturation velocity and high breakdown voltage, have not been fully exploited. Further effort are being done on the investigation of the function of polarization effect, which is unique property of III-nitrides, in the two-dimensional carrier transport of heterostructure. Deep comprehension on the relationship between the material properties and the transport mechanism in low-dimentional heterostructure turns out to be crucial for the development of next generation GaN devices and integrated circuits. This project aims at understanding the physics behind the electrical characteristics in low-dimentional III-nitrides heterosturcture. The two-dimensional carrier transport properties would be extensivly investigated with different quantum well structure, subband distribution and the electron state under different operation. The saturation mechanism of the electron velocity in low-dimensional heterostructure, which is distinctly different to that in the bulk material, would be disclosed. Based on the polarization and two-dimensional energy band engineering, optimum GaN-based heterostructure with improved electron saturation velocity will be designed, by which a GaN HFET device with ft≥200GHz is being developed. This work would be of great importance for expansion of III-nitride applications and provide a strong physical foundation for the development of new generaton high frequency device and circuits technology.