Achieving low ON-resistance in E-mode regrown U-shaped p-GaN gate multi-channel HEMT

Abstract

This work demonstrates an E-mode regrown U-shaped p-GaN gate multi-channel HEMT on a sapphire substrate. The multi-channel access region is favorable to reducing the ON-resistance (RON). E-mode operation was achieved by locally etching through the multiple channels at the gate region and regrowing a p-GaN/AlGaN/GaN gate stack. The currents from multi-channel region merge into the gated channel through the regrown GaN layer. To study the effectiveness of the current merging mechanism, I–V characterization and transmission line method analysis have been conducted. The fabricated device with LGD of 52 μm presents a positive threshold voltage (VTH) of 1.8 V and a low RON of 21.6 Ω mm, corresponding to a specific resistance (RON,SP) of 13.82 mΩ cm2. The resistance of transition region where the multi-channel currents merge into the gated channel is found to account for 34% of the total RON. Temperature-dependent I–V characteristics of the device were investigated. At 150 °C, the percentage of the transition region resistance drops to 11%. The device presents competitive RON–LGD performance among the state-of-the-art GaN devices. These results validate the proposed U-shaped p-GaN gate multi-channel HEMT as a promising approach to reduce the RON of E-mode GaN power devices scaling up (i.e., with larger LGD) for wider operation voltage range.