Breakdown voltage enhancement for power AlGaN/GaN HEMTs with Air-bridge Field Plate

An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected Air-bridge Field Plate (AFP) is simulated, optimized and experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between gate and drain. The fabrication process is based on a commercially available RF GaN on SiC technology. Device characteristics for this work were optimized via layout changes only. An extensive analysis on the surface electrical field distribution was used to study the effect of varying AFP dimension. Simulation results indicated a breakdown voltage of 425 V for the AFP device can be achieved at V_GS = -5 V. The gate to drain distance is 6 μm and the gate length is 0.8 μm. The fabricated results for AFP device are in relatively good agreement with the simulation results and exhibit improvement in forward blocking voltage of 375 V at V_GS = -5 V. This is a factor of 3× improvement when compared to the best device that can be fabricated using conventional field plate (FP) for this particular process. The measured specific on-resistance for the device with the proposed AFP is 0.58 mΩ·cm² at V_GS = 0 V, which compares favorably with 0.79 mΩ·cm² for the device with a conventional FP.