On the Onset of Breakdown of the Virtual Gate in AlGaN/GaN HEMTs

A physical model is proposed, which explains the breakdown of the virtual gate region. The onset of this phenomenon is explained by impact ionization, which is subsequently controlled through the multiphonon assisted ionization of surface traps in the presence of an electric field. The energetic distribution of surface traps on the top AlGaN surface effectively explains the kink contour in a full range of output
${I}-{V}$
characteristics. A virtual gate model has also been proposed to include realistic real-time characteristics of surface states that mimic trapped charge and conductivity with metallic gate simultaneously. The reduction in barrier height of the virtual gate due to leakage current results into its breakdown. The physical model of output
${I}-{V}$
clearly explains the complex contour of kink present in AlGaN/GaN HEMTs at all gate voltages.