%A Sheng-Lei Zhao(赵胜雷), Zhi-Zhe Wang(王之哲), Da-Zheng Chen(陈大正), Mao-Jun Wang(王茂俊), Yang Dai(戴扬), Xiao-Hua Ma(马晓华), Jin-Cheng Zhang(张进成), Yue Hao(郝跃) %T 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor %0 Journal Article %D 2019 %J Chin. Phys. B %R 10.1088/1674-1056/28/2/027301 %P 27301-027301 %V 28 %N 2 %U {https://cpb.iphy.ac.cn/CN/abstract/article_121428.shtml} %8 2019-02-05 %X In this paper, we present a 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor (DH HEMT) with a gate-drain spacing LGD=18.8 μm. Compared with the regular DH HEMT, our circular structure has a high average breakdown electric-field strength that increases from 0.42 MV/cm to 0.96 MV/cm. The power figure of merit VBR2/RON for the circular HEMT is as high as 1.03×109 V2·Ω-1·cm-2. The divergence of electric field lines at the gate edge and no edge effect account for the breakdown enhancement capability of the circular structure. Experiments and analysis indicate that the circular structure is an effective method to modulate the electric field.