High-performance enhancement-mode AlGaN/GaN HEMTs using fluoride-based plasma treatment

• Published in: IEEE electron device letters 2005-07, Vol.26 (7), p.435-437
• Main Authors: Yong Cai, Yugang Zhou, Chen, K.J., Lau, K.M.
• Format: Article
• Language: English
• Subjects: AlGaN/GaN; Aluminum gallium nitride; Aluminum gallium nitrides; Annealing; Applied sciences; Cutoff frequency; D-HEMTs; Drains; Electronics; enhancement mode; Exact sciences and technology; Fabrication; fluoride; Gallium nitride; Gallium nitrides; Gates; HEMTs; High electron mobility transistors; high-electron mobility transistor (HEMT); Leakage current; MODFETs; Plasma temperature; plasma treatment; Rapid thermal annealing; Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Threshold voltage; Transistors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2005.851122

We report a novel approach in fabricating high-performance enhancement mode (E-mode) AlGaN/GaN HEMTs. The fabrication technique is based on fluoride-based plasma treatment of the gate region in AlGaN/GaN HEMTs and post-gate rapid thermal annealing with an annealing temperature lower than 500/spl deg/C. Starting with a conventional depletion-mode HEMT sample, we found that fluoride-based plasma treatment can effectively shift the threshold voltage from -4.0 to 0.9 V. Most importantly, a zero transconductance (g/sub m/) was obtained at V/sub gs/=0 V, demonstrating for the first time true E-mode operation in an AlGaN/GaN HEMT. At V/sub gs/=0 V, the off-state drain leakage current is 28 μA/mm at a drain-source bias of 6 V. The fabricated E-mode AlGaN/GaN HEMTs with 1 μm-long gate exhibit a maximum drain current density of 310 mA/mm, a peak g/sub m/ of 148 mS/mm, a current gain cutoff frequency f T of 10.1 GHz and a maximum oscillation frequency f max of 34.3 GHz.