On-State Critical Gate Overdrive Voltage For Fluorine-Implanted Enhancement-Mode Algan/Gan High Electron Mobility Transistors

This paper presents a study of the ON-state gate overdrive of enhancement-mode AlGaN/GaN HEMTs fabricated by fluorine plasma implantation technology. A critical gate forward voltage (VGC) is observed, beyond which the channel turn-on voltage (or threshold voltage) of the devices exhibits a persistent and nonrecoverable negative shift. This phenomenon is explained by a proposed physical model based on the impact ionization of the F ions in the barrier layer by hot electron injection. The proposed physical model is further validated by the temperature-dependent characterization of VGC that shows an eventual stabilization at higher temperatures (> 125 degrees C), owing to the efficient relaxation of hot electrons by phonon scattering. The determination of VGC provides valuable guideline for the design of gate drive circuits of GaN power circuits (C) 2011 American Institute of Physics. [doi:10.1063/1.3664912]