GaN-based HEMT featuring AlGaN/p-GaN stacked gate layers and oxidized Ni gate electrode with threshold voltages exceeding 3 V

Abstract To realize a high threshold power transistor on a GaN chip alone, we have developed a GaN-based HEMT featuring AlGaN/p-GaN stacked gate layers and oxidized Ni gate electrodes. Experimental results show the threshold voltage increases with the aluminium composition ratio of the AlGaN gate layer, reaching 3.5 V at 0.20 Al ratio. Additionally, samples with more strongly oxidized Ni gates exhibited an even higher threshold voltage of 5.2 V and very low gate current during on-state. These results suggest that the AlGaN gate layer and oxidized Ni gate play a crucial role for high threshold voltage and low gate current.