Threshold voltage control by gate oxide thickness in fluorinated GaN metal-oxide-semiconductor high-electron-mobility transistors

• Main Authors: Zhang, Yuhao (Contributor), Sun, Min (Contributor), Jayanta Joglekar, Sameer (Contributor), Fujishima, Tatsuya (Contributor), Palacios, Tomas (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science (Contributor), Massachusetts Institute of Technology. Department of Materials Science and Engineering (Contributor), Massachusetts Institute of Technology. Microsystems Technology Laboratories (Contributor)
• Format: Article
• Language: English
• Published: American Institute of Physics (AIP), 2018-06-06T19:28:13Z.
• Subjects: Article
• Online Access: Get fulltext

This paper demonstrates the compensation of the intrinsic positive charges in Al₂O₃ gate dielectric by fluorine ions in GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs). Negatively-charged fluorine ions diffused into the oxide from the AlGaN barrier during the 250 °C atomic layer deposition compensate the intrinsic positive charge present in the Al₂O₃. This compensation is key to control the threshold voltage (Vth) of enhancement-mode (E-mode) transistors. A comprehensive analytical model for the V[subscript th] of fluorinated MOS-HEMTs was established and verified by experimental data. This model allows the calculation of the different charge components in order to optimize the transistor structure for E-mode operation. Using the proposed charge compensation, the V[subscript th] increases with gate dielectric thickness, exceeding 3.5V for gate dielectrics 25 nm thick.