Electric Field Modulation in the Channel by Lateral Thickness Distribution of High-k Films Formed on GaN HEMTs to Improve Breakdown Voltage

High breakdown voltage owing to a quasi-uniform electric field, upon loading a high-
${k}$
film in the gate–drain region, was recently investigated. However, the uniform high-
${k}$
film has a limit to modulate the electric field distribution, and the electric field near the gate side is stronger than that near the drain side. This study proposes the modulation of the high-
${k}$
film thickness between the drain and gate of a gallium nitride (GaN) high electron mobility transistor (HEMT) in the lateral direction for electric field distribution control in the channel. Compared to a uniform film, the electric field near the gate can also be weakened and possesses a negative gradient compared to a conventional electric field slope. Based on the simulation results, the voltage at which impact ionization occurs can be increased by 20%. This can be explained using the smaller gate leakage current and improved electric field distribution. Furthermore, the maximum electric field increased in the present structure when the slope of the electric field was negative.