Breakdown-Voltage-Enhancement Technique for RF-Based AlGaN/GaN HEMTs With a Source-Connected Air-Bridge Field Plate

• Published in: IEEE electron device letters 2012-05, Vol.33 (5), p.670-672
• Main Authors: Gang Xie, Xu, E., Junmin Lee, Hashemi, N., Bo Zhang, Fu, F. Y., Wai Tung Ng
• Format: Article
• Language: English
• Subjects: Air bridge; AlGaN/GaN high-electron-mobility transistor (HEMT); Aluminum gallium nitride; Applied sciences; breakdown voltage; Electrical engineering. Electrical power engineering; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; field plate (FP); Gallium nitride; GaN power devices; HEMTs; Leakage current; Logic gates; MODFETs; Power electronics, power supplies; Radio frequency; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2012.2188492

An AlGaN/GaN high-electron-mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is proposed. The device features a metal field plate (FP) that jumps from the source over the gate region and lands between the gate and drain. The fabrication process is based on a commercially available radio-frequency GaN-on-SiC technology. Device characteristics for this work were optimized via layout changes only. When compared to a similar-sized HEMT device with a conventional FP structure, the AFP not only minimizes the parasitic gate-to-source capacitance but also exhibits a higher off-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate-to-drain distance of 6 μm and a gate length of 0.8 μm, a three-times-higher forward blocking voltage of 375 V was obtained at V GS = -5 V. In contrast, a similar-sized HEMT with a conventional FP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. The specific on-resistance for the device with the proposed AFP is 0.58 mΩ·cm 2 at V GS = 0 V, which compares favorably with 0.79 mΩ·cm 2 for the best device with a conventional FP.